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Retrograde Degeneration in the Optic Nerves and Tracts
RETROGRADE DEGENERATION IN THE OPTIC NERVES AND TRACTS A N EXPERIMENTAL STUDY OF CHANGES IN THE AXIS CYLINDERS* P. J. LEINFELDER,
M.D.
Iowa City, Iowa The ocurrence of retrograde degenera tion in the optic nerve following its sec tion has long been a source of discussion (Birch-Hirschfeld, 1 Ramon y Cajal 2 ). In a previous paper, 3 certain aspects of retrograde degeneration occurring in the optic nerve and retina following section of the optic tracts and optic nerve were reported. These studies showed that very active demyelinization occurred in the nerve fibers of the optic nerve posterior transection, but following section of both tracts only slight damage to the myelin of the optic nerves was observed. This would indicate two possibilities: either the optic nerves are immune to degenera tion following tract lesions, or demyelini zation gradually diminishes distal to the lesion and therefore is minimal or ab sent in the optic nerves. In support of the latter contention is the observation that degeneration after a posterior lesion of the optic tract decreased in extent as the chiasm was approached.
section was performed at the chiasma by the temporal operative approach. Vari ous periods of time were allowed to elapse prior to histologic investigation of the degenerating tissues. Since it was particularly desirable to determine the reaction in the axis cylinders, Bodian's 5 silver stain was used most extensively. In some instances Marchi or Held stains were used to confirm the presence and extent of degenerative changes in the myelin. Electrolytic Section of the Optic Tracts One or both optic tracts were sectioned with the stereotaxic instrument according to the technique previously reported. Four cats and six monkeys were used in the experiments. Tissue was prepared from the animals after periods of from 5 to 60 days. Silver and Marchi or Held stains were made of tissue obtained from the optic nerves and tracts. Section of Optic Tracts Anteriorly
EXPERIMENTAL
In order to gain further information concerning the phenomenon of degenera tion, additional experiments were made on cats and monkeys. The optic tracts were sectioned anteriorly in several ani mals by means of the Horsley-Clark 4 stereotaxic instrument, and optic-nerve * This work is a portion of research studies in neuro-ophthalmology being made in the De partment of Ophthalmology of the University of Iowa under a grant from the American Academy of Ophthalmology and Otolaryngology. Read before the Ophthalmic Section at the Forty-fourth Annual Meeting of the American Academy of Ophthalmology and Otolaryngology, in Chicago, October, 1939. 796
Successful anterior section of the optic tracts (table 1) was made in three mon keys and one cat. In cat C645 both tracts showed extensive degeneration 10 days after section, but the axis cylinders in each optic nerve were entirely normal. The lesion in this animal was made within 2 mm. of the optic chiasm, and the tracts showed great degeneration above the lesion. Marchi studies of the nerves revealed disintegration of the mye lin that was much greater in the posterior portion than in the anterior (figs. 1 and 2). In the monkey M612, five days after section of the tracts, there was likewise no degeneration in the axis cylinders of
E X P E R I M E N T A L CHANGES IN AXIS CYLINDERS
797
TABLE 1 DEGENERATION RESULTING FROM ANTERIOR OPTIC TRACT LESIONS
Time
Osmic Acid
Silver Tract Right Left
Nerve Right Left
Tract Right Left
Nerve Right Left
Lesion
Lesion
+ + ++ +++ + + +++ +++
M612
5
80
85
n
C645
10
85
85
n Anterior n n Posterior n
85 85
80 80
M624
12
25
20
si. si.
si. si.
25 30
15 25
M629
60
n
50
++ ++
++ ++
n n
40 40
n
sector+ sector+
+
+
si. si.
si. si.
the nerves. After 12 days there was no further change, and the axis cylinder remained normal. After 60 days, M629 showed some decrease in the number of axis cylinders in the optic nerve, but the usual degenerative phe nomena were absent (dissolution of the entire axis cylinder and myelin sheath structures). Held stain confirmed this reduction in the number of nerve fibers pres ent. Section of Optic Tracts Posteri orly
Fig. 1 (Leinfelder). Typical degeneration in optic tract following tract lesion ( M a r c h i ) .
Posterior lesions in the tracts (table 2) were accomplished in three cats and three monkeys. Sections for study
were made at intervals between 20 and 32 days after operation.
Fig. 2 (Leinfelder). Degenera tion in posterior and anterior por tions of optic nerve following anterior section of optic tract ( M a r c h i ) .
P. J. LEINFELUEK
798
TABLE 2 DEGENERATION RESULTING FROM POSTERIOR OPTIC TRACT LESIONS Silver Time
Tract Right Left
C616
4
C632
20
65 80
80 95
M628
21
n n
C639
23
M627 M62S
Osmic Acid Nerve Right Left
n
Tract Right Left
Nerve Right Left
90
90
si.
si.
+
+
n
65 80
80 95
tr.
tr.
5 10
n n
n n
n n
5 15
n n
n n
15 30
90 100
n n
n n
15 15
85 85
n
n
24
n n
50 90
+
+ thinned si.
s!.
n n
50 100
(r.+
tr.
32
n r>
40 50
+ sector si. +-(-thinning ■si.
n n
50 60
I n cat C632, successful lesions in both tracts resulted in practically complete degeneration in the posterior tracts, some what less in the anterior tracts, but no demonstrable degeneration of the axis cylinders in the optic nerves. Only slight degeneration was observed in the optic nerves with osmic-acid stain, yet great changes were present in the myelin sheaths of the optic tracts.
very slight
In the tissue from other animals, a similarity in reaction was observed. E x tensive degeneration was present in the posterior tract, to a considerably less de gree it occurred in the anterior tract, but only a decrease in the number of axis cylinders could be observed in the optic nerves. Although the decrease in the num ber of nerve fibers was generalized, the thinning was more extensive in certain areas or sectors. Evidence of degeneration was less apparent in the anterior nerves than in the posterior portion.
Fig. 3 (Leinfelder). Complete primary degeneration in optic nerve following its anterior section (Silver).
Osmic-acid preparations showed only slight degenera tion in the optic nerves but ex tensive change in the optic tracts. It was likewise noted that in the osmic-acid prepara tions there was less evidence of reaction in the anterior por tion of the nerve than in the posterior. It is definitely ap parent that in all of these ani mals the amount of degenera tion in the optic nerves, wheth er shown by silver, osmic acid, or the Held stain, is of little
EXPERIMENTAL CHANGES IN AXIS CYLINDERS significance when compared with the ex tensive changes in the optic tracts.
TABLE 4 DEGENERATION RESULTING FROM POSTERIOR CPTIC NERVE SECTIONS
Section of the Optic Nerve Anteriorly In six animals, four cats and two mon keys (table 3 ) , the optic nerve was sec-
10
C611
14
C630
14
Nerve Right Left
C613
15
+ -(-anterior -(+ -(-posterior +
100 100
C691
20
++ ++ ++ ++ ++ ++ ++ ++ ++ ++
100 100
C603
30
100 100
C669
75
TABLE 3
Time C608 C621
10
C626
18
M633
20
C634
21
M500
87
Time Ml
DEGENERATION RESULTING FROM ANTERIOR OPTIC NERVE SECTIONS
Silver Stain Tract Right Left
+ + + + + + + + + +
foo
100 100 100 100 100
tioned in the orbit, and in one cat the retina was removed from one eye. These experiments were performed in order to
799
Silver Stain Tract Right Left
++ ++ ++ ++ ++ ++ + + ++ ++ + + ++ ++
+ + + + + + ++ ++ + + ++ ++ + +
Nerve Right Left swollen swollen
n 30 30 20 40
20 50
n n
si.
50 80
+
ing from the brain through the optic nerve. T h e optic nerves of all animals showed complete degeneration of the axis cylin ders (fig. 3) throughout the extent of the nerve. I n the tracts the degeneration was partial because of the incomplete crossing that occurs in the chiasm. N o evidence of efferent fibers could be ob-
Fig. 4 (Leinfelder). Normal left and right posterior optic nerves 14 days after section of left optic nerve posteriorly (Silver). show the primary degenerative changes in the optic nerve and to demonstrate, if possible, efferent fibers that might be pass-
tained with the silver stain. Likewise as would be expected, there was no degeneration in the opposite uninjured nerve.
800
P. J, L E I N F E L D E R
Section of the Optic Nerve Posteriorly In seven animals, one monkey and six cats (table 4 ) , the optic nerve was sec-
operation was an apparent swelling of the axis cylinders in the posterior sections of the nerve. The optic tracts showed den-
Fig. S (Leinfelder). Typical primary degeneration in optic tract following optic-nerve section (Silver).
tioned immediately anterior to the chiasm. After periods of time (10 to 75 days), preparations were made of the optic
nite evidence of disintegration of the axis cylinders. In cat C611 silver staining disclosed no evidence of change in the axis
Fig. 6 (Leinfelder). Posterior and anterior of left optic nerve 75 days after its posterior section (Silver).
nerves and tracts. Staining was with silver, osmic acid, and the Held method. In monkey Ml the only evidence of degeneration in the optic nerves 10 days after
cylinders of the optic nerves, while extensive degeneration had occurred in the optic tracts (figs. 4 and 5). However, after time intervals of 30 and 75 days
EXPERIMENTAL CHANGES IN AXIS CYLINDERS
following operation, there was rather ex tensive degeneration of the axis cylinders in the posterior portion of the nerve, but less marked involvement of the anterior portion (fig. 6). DISCUSSION
The data from all experiments, except section of the optic nerve anteriorly, show much greater degeneration in the optic tracts than is present in the optic nerves. This at first would seem to indicate that the degree of degeneration is in some part at least dependent upon a difference in structure between the tracts and the nerves. Yet it is apparent that there is a greater degree of degeneration in the optic nerve following its posterior section than occurs in it after anterior or pos terior-tract section. Likewise posterior section of the optic tract results in less intense degeneration in the chiasmic re gion of the tract than is present at higher levels. It is possible that the greater de gree of retrograde degeneration in the nerve following posterior section is, in part at least, due to surgical interference with its vascular supply. That the retrograde degenerative phe nomena are different from the primary type is well shown in tables 3 and 4. Sec tion of the optic nerve anteriorly is rap idly followed by complete disintegration of both myelin sheaths and axis cylinders, whereas a posterior section causes no ob servable early change in the axis cylinder, and later results in only incomplete de generation. It is peculiar that posterior section of the optic nerve eventually re sults in a retrograde degeneration that in part bears a resemblance to primary de generation—increased homogeneity. This phenomenon does not occur after tract lesions. It appears, therefore, that retrograde degeneration is of an incomplete nature and that, as recognized by Boeke15 for
801
nerve fibers in general, it usually extends only a few segments from the lesion but occasionally a fiber may disintegrate com pletely. The present experiments seem to indicate that visual fibers react in the same manner. The impression is gained that the extent of retrograde degeneration in the optic nerve is a phenomenon that is dependent upon the distance of the lesion from the nerve cell, just as it is with nerves in general. Thus a lesion near the lateral geniculate body in the tract results in little retrograde degeneration in the optic-nerve fibers, while a lesion in the optic nerve results in far greater destruction of the axis cylinders. The degeneration of some of the nerve fibers, even after distant injury, is inter esting. It is known that any injury to the axon results in a chromatolytic change in the ganglion cell (Nissl 7 ). The more severe the injury or the closer to the nerve cell that it occurs, the more severe will be the reaction of chromatolysis (Bielschowsky 8 ). Birch-Hirschfeld pointed out that many retinal ganglion cells were only temporarily injured by the chromatolytic process, and that ex cept for an increase in the Nissl sub stance, they eventually returned to nor mal. Many cells however completely dis integrate. The reduction in number of ganglion cells was confirmed by James 9 and in a previous paper of the author. Although a report of the study of the retinas is not included in this paper, the ganglion cells were observed in most spe cimens, and the reduction in number was never obvious after section of the optic tracts, but was definite after posterior sec tion of the nerve. James observed a marked reduction in the number of cells after anterior section of the optic nerve. It appears therefore that the disappear ance of the nerve fibers in retrograde degeneration occurs following, and as a result of, the death and disappearance of
802
P. J. LEINFELDER
the ganglion cells. T h e incomplete nature of the degeneration along with its late development appears to substantiate this theory. This work, therefore, indicates that the visual pathway is not peculiar in its reac-
tion to degeneration but that, like nerves or afferent tracts, it reacts jury by retrograde degeneration is in proportion to the extent of and to the distance of the injury the nerve cell.
other to inwhich injury from
BIBLIOGRAPHY 1
Birch-Hirschfeld. Beitrag zur Kenntnis der Netzhautganglionzellen unter physiologischen und pathologischen Verhaltnissen. Arch. f. Ophth., 1900, v. 50, p. 166. Ramon y Cajal, S. Degeneration and regeneration of the nervous system. Translated by R. M. May. London, Oxford University Press, 1928, v. 2, p. 594. 3 Leinfelder, P. J. Retrograde degeneration in the optic nerves and retinal ganglion cells. Trans. Amer. Ophth. Soc, 1938, v. 36, p. 307. 4 Horsley, V., and Clark, R. H. The structure and function of the cerebellum examined by a new method. Brain, 1908, v. 31, p. 45. " Bodian, David. A new method for staining nerve fibers and nerve endings in mounted paraffin sections. Anat. Rec, 1936, v. 65, p. 89. s Boeke, J. In Bumke and Foerster's Handbuch der Neurologic Berlin, Julius Springer, 1935, v. 1, p. 1010. 1 Nissl, F. Ueber die Veriinderungen der Nervenzellen am Facialiskern des Kaninchens nach Ausreissung der Nerven. Allg. Zeit. f. Psychiat., 1891-1892, v. 48, p. 197. 8 Bielschowsky, M. In Bumke and Foerster's Handbuch der Neurologie. Berlin, Julius Springer, 1935, v. 1, p. 155. "James, G. R. Degeneration of ganglion cell following axonal injury. Arch, of Ophth., 1933, v. 9, p. 338. 2
M.D.
Iowa City, Iowa The ocurrence of retrograde degenera tion in the optic nerve following its sec tion has long been a source of discussion (Birch-Hirschfeld, 1 Ramon y Cajal 2 ). In a previous paper, 3 certain aspects of retrograde degeneration occurring in the optic nerve and retina following section of the optic tracts and optic nerve were reported. These studies showed that very active demyelinization occurred in the nerve fibers of the optic nerve posterior transection, but following section of both tracts only slight damage to the myelin of the optic nerves was observed. This would indicate two possibilities: either the optic nerves are immune to degenera tion following tract lesions, or demyelini zation gradually diminishes distal to the lesion and therefore is minimal or ab sent in the optic nerves. In support of the latter contention is the observation that degeneration after a posterior lesion of the optic tract decreased in extent as the chiasm was approached.
section was performed at the chiasma by the temporal operative approach. Vari ous periods of time were allowed to elapse prior to histologic investigation of the degenerating tissues. Since it was particularly desirable to determine the reaction in the axis cylinders, Bodian's 5 silver stain was used most extensively. In some instances Marchi or Held stains were used to confirm the presence and extent of degenerative changes in the myelin. Electrolytic Section of the Optic Tracts One or both optic tracts were sectioned with the stereotaxic instrument according to the technique previously reported. Four cats and six monkeys were used in the experiments. Tissue was prepared from the animals after periods of from 5 to 60 days. Silver and Marchi or Held stains were made of tissue obtained from the optic nerves and tracts. Section of Optic Tracts Anteriorly
EXPERIMENTAL
In order to gain further information concerning the phenomenon of degenera tion, additional experiments were made on cats and monkeys. The optic tracts were sectioned anteriorly in several ani mals by means of the Horsley-Clark 4 stereotaxic instrument, and optic-nerve * This work is a portion of research studies in neuro-ophthalmology being made in the De partment of Ophthalmology of the University of Iowa under a grant from the American Academy of Ophthalmology and Otolaryngology. Read before the Ophthalmic Section at the Forty-fourth Annual Meeting of the American Academy of Ophthalmology and Otolaryngology, in Chicago, October, 1939. 796
Successful anterior section of the optic tracts (table 1) was made in three mon keys and one cat. In cat C645 both tracts showed extensive degeneration 10 days after section, but the axis cylinders in each optic nerve were entirely normal. The lesion in this animal was made within 2 mm. of the optic chiasm, and the tracts showed great degeneration above the lesion. Marchi studies of the nerves revealed disintegration of the mye lin that was much greater in the posterior portion than in the anterior (figs. 1 and 2). In the monkey M612, five days after section of the tracts, there was likewise no degeneration in the axis cylinders of
E X P E R I M E N T A L CHANGES IN AXIS CYLINDERS
797
TABLE 1 DEGENERATION RESULTING FROM ANTERIOR OPTIC TRACT LESIONS
Time
Osmic Acid
Silver Tract Right Left
Nerve Right Left
Tract Right Left
Nerve Right Left
Lesion
Lesion
+ + ++ +++ + + +++ +++
M612
5
80
85
n
C645
10
85
85
n Anterior n n Posterior n
85 85
80 80
M624
12
25
20
si. si.
si. si.
25 30
15 25
M629
60
n
50
++ ++
++ ++
n n
40 40
n
sector+ sector+
+
+
si. si.
si. si.
the nerves. After 12 days there was no further change, and the axis cylinder remained normal. After 60 days, M629 showed some decrease in the number of axis cylinders in the optic nerve, but the usual degenerative phe nomena were absent (dissolution of the entire axis cylinder and myelin sheath structures). Held stain confirmed this reduction in the number of nerve fibers pres ent. Section of Optic Tracts Posteri orly
Fig. 1 (Leinfelder). Typical degeneration in optic tract following tract lesion ( M a r c h i ) .
Posterior lesions in the tracts (table 2) were accomplished in three cats and three monkeys. Sections for study
were made at intervals between 20 and 32 days after operation.
Fig. 2 (Leinfelder). Degenera tion in posterior and anterior por tions of optic nerve following anterior section of optic tract ( M a r c h i ) .
P. J. LEINFELUEK
798
TABLE 2 DEGENERATION RESULTING FROM POSTERIOR OPTIC TRACT LESIONS Silver Time
Tract Right Left
C616
4
C632
20
65 80
80 95
M628
21
n n
C639
23
M627 M62S
Osmic Acid Nerve Right Left
n
Tract Right Left
Nerve Right Left
90
90
si.
si.
+
+
n
65 80
80 95
tr.
tr.
5 10
n n
n n
n n
5 15
n n
n n
15 30
90 100
n n
n n
15 15
85 85
n
n
24
n n
50 90
+
+ thinned si.
s!.
n n
50 100
(r.+
tr.
32
n r>
40 50
+ sector si. +-(-thinning ■si.
n n
50 60
I n cat C632, successful lesions in both tracts resulted in practically complete degeneration in the posterior tracts, some what less in the anterior tracts, but no demonstrable degeneration of the axis cylinders in the optic nerves. Only slight degeneration was observed in the optic nerves with osmic-acid stain, yet great changes were present in the myelin sheaths of the optic tracts.
very slight
In the tissue from other animals, a similarity in reaction was observed. E x tensive degeneration was present in the posterior tract, to a considerably less de gree it occurred in the anterior tract, but only a decrease in the number of axis cylinders could be observed in the optic nerves. Although the decrease in the num ber of nerve fibers was generalized, the thinning was more extensive in certain areas or sectors. Evidence of degeneration was less apparent in the anterior nerves than in the posterior portion.
Fig. 3 (Leinfelder). Complete primary degeneration in optic nerve following its anterior section (Silver).
Osmic-acid preparations showed only slight degenera tion in the optic nerves but ex tensive change in the optic tracts. It was likewise noted that in the osmic-acid prepara tions there was less evidence of reaction in the anterior por tion of the nerve than in the posterior. It is definitely ap parent that in all of these ani mals the amount of degenera tion in the optic nerves, wheth er shown by silver, osmic acid, or the Held stain, is of little
EXPERIMENTAL CHANGES IN AXIS CYLINDERS significance when compared with the ex tensive changes in the optic tracts.
TABLE 4 DEGENERATION RESULTING FROM POSTERIOR CPTIC NERVE SECTIONS
Section of the Optic Nerve Anteriorly In six animals, four cats and two mon keys (table 3 ) , the optic nerve was sec-
10
C611
14
C630
14
Nerve Right Left
C613
15
+ -(-anterior -(+ -(-posterior +
100 100
C691
20
++ ++ ++ ++ ++ ++ ++ ++ ++ ++
100 100
C603
30
100 100
C669
75
TABLE 3
Time C608 C621
10
C626
18
M633
20
C634
21
M500
87
Time Ml
DEGENERATION RESULTING FROM ANTERIOR OPTIC NERVE SECTIONS
Silver Stain Tract Right Left
+ + + + + + + + + +
foo
100 100 100 100 100
tioned in the orbit, and in one cat the retina was removed from one eye. These experiments were performed in order to
799
Silver Stain Tract Right Left
++ ++ ++ ++ ++ ++ + + ++ ++ + + ++ ++
+ + + + + + ++ ++ + + ++ ++ + +
Nerve Right Left swollen swollen
n 30 30 20 40
20 50
n n
si.
50 80
+
ing from the brain through the optic nerve. T h e optic nerves of all animals showed complete degeneration of the axis cylin ders (fig. 3) throughout the extent of the nerve. I n the tracts the degeneration was partial because of the incomplete crossing that occurs in the chiasm. N o evidence of efferent fibers could be ob-
Fig. 4 (Leinfelder). Normal left and right posterior optic nerves 14 days after section of left optic nerve posteriorly (Silver). show the primary degenerative changes in the optic nerve and to demonstrate, if possible, efferent fibers that might be pass-
tained with the silver stain. Likewise as would be expected, there was no degeneration in the opposite uninjured nerve.
800
P. J, L E I N F E L D E R
Section of the Optic Nerve Posteriorly In seven animals, one monkey and six cats (table 4 ) , the optic nerve was sec-
operation was an apparent swelling of the axis cylinders in the posterior sections of the nerve. The optic tracts showed den-
Fig. S (Leinfelder). Typical primary degeneration in optic tract following optic-nerve section (Silver).
tioned immediately anterior to the chiasm. After periods of time (10 to 75 days), preparations were made of the optic
nite evidence of disintegration of the axis cylinders. In cat C611 silver staining disclosed no evidence of change in the axis
Fig. 6 (Leinfelder). Posterior and anterior of left optic nerve 75 days after its posterior section (Silver).
nerves and tracts. Staining was with silver, osmic acid, and the Held method. In monkey Ml the only evidence of degeneration in the optic nerves 10 days after
cylinders of the optic nerves, while extensive degeneration had occurred in the optic tracts (figs. 4 and 5). However, after time intervals of 30 and 75 days
EXPERIMENTAL CHANGES IN AXIS CYLINDERS
following operation, there was rather ex tensive degeneration of the axis cylinders in the posterior portion of the nerve, but less marked involvement of the anterior portion (fig. 6). DISCUSSION
The data from all experiments, except section of the optic nerve anteriorly, show much greater degeneration in the optic tracts than is present in the optic nerves. This at first would seem to indicate that the degree of degeneration is in some part at least dependent upon a difference in structure between the tracts and the nerves. Yet it is apparent that there is a greater degree of degeneration in the optic nerve following its posterior section than occurs in it after anterior or pos terior-tract section. Likewise posterior section of the optic tract results in less intense degeneration in the chiasmic re gion of the tract than is present at higher levels. It is possible that the greater de gree of retrograde degeneration in the nerve following posterior section is, in part at least, due to surgical interference with its vascular supply. That the retrograde degenerative phe nomena are different from the primary type is well shown in tables 3 and 4. Sec tion of the optic nerve anteriorly is rap idly followed by complete disintegration of both myelin sheaths and axis cylinders, whereas a posterior section causes no ob servable early change in the axis cylinder, and later results in only incomplete de generation. It is peculiar that posterior section of the optic nerve eventually re sults in a retrograde degeneration that in part bears a resemblance to primary de generation—increased homogeneity. This phenomenon does not occur after tract lesions. It appears, therefore, that retrograde degeneration is of an incomplete nature and that, as recognized by Boeke15 for
801
nerve fibers in general, it usually extends only a few segments from the lesion but occasionally a fiber may disintegrate com pletely. The present experiments seem to indicate that visual fibers react in the same manner. The impression is gained that the extent of retrograde degeneration in the optic nerve is a phenomenon that is dependent upon the distance of the lesion from the nerve cell, just as it is with nerves in general. Thus a lesion near the lateral geniculate body in the tract results in little retrograde degeneration in the optic-nerve fibers, while a lesion in the optic nerve results in far greater destruction of the axis cylinders. The degeneration of some of the nerve fibers, even after distant injury, is inter esting. It is known that any injury to the axon results in a chromatolytic change in the ganglion cell (Nissl 7 ). The more severe the injury or the closer to the nerve cell that it occurs, the more severe will be the reaction of chromatolysis (Bielschowsky 8 ). Birch-Hirschfeld pointed out that many retinal ganglion cells were only temporarily injured by the chromatolytic process, and that ex cept for an increase in the Nissl sub stance, they eventually returned to nor mal. Many cells however completely dis integrate. The reduction in number of ganglion cells was confirmed by James 9 and in a previous paper of the author. Although a report of the study of the retinas is not included in this paper, the ganglion cells were observed in most spe cimens, and the reduction in number was never obvious after section of the optic tracts, but was definite after posterior sec tion of the nerve. James observed a marked reduction in the number of cells after anterior section of the optic nerve. It appears therefore that the disappear ance of the nerve fibers in retrograde degeneration occurs following, and as a result of, the death and disappearance of
802
P. J. LEINFELDER
the ganglion cells. T h e incomplete nature of the degeneration along with its late development appears to substantiate this theory. This work, therefore, indicates that the visual pathway is not peculiar in its reac-
tion to degeneration but that, like nerves or afferent tracts, it reacts jury by retrograde degeneration is in proportion to the extent of and to the distance of the injury the nerve cell.
other to inwhich injury from
BIBLIOGRAPHY 1
Birch-Hirschfeld. Beitrag zur Kenntnis der Netzhautganglionzellen unter physiologischen und pathologischen Verhaltnissen. Arch. f. Ophth., 1900, v. 50, p. 166. Ramon y Cajal, S. Degeneration and regeneration of the nervous system. Translated by R. M. May. London, Oxford University Press, 1928, v. 2, p. 594. 3 Leinfelder, P. J. Retrograde degeneration in the optic nerves and retinal ganglion cells. Trans. Amer. Ophth. Soc, 1938, v. 36, p. 307. 4 Horsley, V., and Clark, R. H. The structure and function of the cerebellum examined by a new method. Brain, 1908, v. 31, p. 45. " Bodian, David. A new method for staining nerve fibers and nerve endings in mounted paraffin sections. Anat. Rec, 1936, v. 65, p. 89. s Boeke, J. In Bumke and Foerster's Handbuch der Neurologic Berlin, Julius Springer, 1935, v. 1, p. 1010. 1 Nissl, F. Ueber die Veriinderungen der Nervenzellen am Facialiskern des Kaninchens nach Ausreissung der Nerven. Allg. Zeit. f. Psychiat., 1891-1892, v. 48, p. 197. 8 Bielschowsky, M. In Bumke and Foerster's Handbuch der Neurologie. Berlin, Julius Springer, 1935, v. 1, p. 155. "James, G. R. Degeneration of ganglion cell following axonal injury. Arch, of Ophth., 1933, v. 9, p. 338. 2