480 the right hemisphere was different from that of the left. The right and the left hands also are perfectly capable of expressing the different and contrary wills of the two hemispheres. The best-known instance was when the first of the patients tied his dressing-gown cord with one hand whilst simultaneously untying it with the other. Even a task as simple as mowing a lawn can be troublesome because one hand steers the mower one way while the other hemisphere wants to push it in another direction. One patient sits on his left hand when reading a book, otherwise the left hand turns over to pages which the left hemisphere is not reading at that time, and the right hand has continuously to correct what the left hand has done. Another patient who observed that her left hand has a mind of its own reports it slapping her on several occasions, as for example when she had overslept or even just while she was watching television. The study of split-brain people is of great importance in telling us about the respective functions of the two sides oj the brain, but more than this the investigations take u right to the heart of the perennial questions of tht nature of consciousness and the nature of will. TOXIC MEGACOLON ASK a group ot clinicians about toxic
megacolon-
dilatation of the large bowel with systemic disturbance and not infrequent progression to perforation-and most will say it is a complication of ulcerative colitis. This, however, is too narrow a view: it is becoming increasingly obvious that any acute inflammatory process in the large bowel may produce the same effect. How this comes about is uncertain, though some years ago Lumb and his colleagues drew attention to the transmural cedema which may interfere with the intrinsic mucosal plexus of the colon and so perhaps compromise motility. Such a pathogenesis must remain speculative because ignorance persists on what normally makes the colon move.
is
Though precise knowledge of the disordered function lacking, recognition that toxic megacolon may compli-
cate onus
any acute colonic inflammation puts an increased on the physician to reach a precise diagnosis.
Lately Schofield, Mandal, and Ironside2 have reminded us that when a patient is diagnosed as having "acute colitis" and is admitted to an infectious-diseases or a general hospital, then three possibilities (at least) arise: primary colonic disease (ulcerative colitis or Crohn’s disease) ; acute salmonella infection; and inflammatory bowel disease complicated by salmonella infection. They might have added, though it is outside their own reported experience, that acute ischaemic colitis and pseudomembranous enterocolitis occasionally give rise to the same clinical picture. Thus "toxic megacolon" is a syndrome in the precise meaning of that word. The admission of a patient with the clinical disorder is a call for two things-firstly, the usual measures to resuscitate and evaluate (fluid and electrolyte replacement, clinical examination, and abdominal X-rays to establish baselines and detect possible peritonitis); secondly, a vigorous attempt to reach a precise diagnosis by a review of previous historical and biopsy evidence, by stool culture, and by a new rectal 1. Lumb, G., Protheroe, R. H. B., Ramsay, G Br. J. Surg 1955, 2 Schofield, P. F., Mandal, B K., Ironside, A. G. ibid 1979, 66, 5.
43, 182.
biopsy submitted to rapid histopathological processing. The cause of toxic megacolon has an important bearing on treatment. If it is ulcerative colitis or Crohn’s disease the patient is unlikely to benefit from non-operative management and requires either subtotal colectomyhighly satisfactory in the hands of skilful surgeons’,’or a "blow-hole"4 which will decompress the colon. When the diseased colon is killing the patient, surgical treatment is an urgent matter: fortunately, many clinicians have now abandoned the notion that resort to surgery is an admission of failure. By contrast, the patient with salmonella infection will get better with intensive fluid and electrolyte therapy and rarely if ever will need operation. In those with acute ischaemic colitis or other ill-defined inflammations experience is small and no ground-rules for management can be laid down. Few surgeons and probably only a few more physicians appreciate the ubiquity in our modern world of salmonellosis. Schofield and his colleagues have reminded us that needless sacrifice of a recoverable colon can be avoided by remembering the salmonella as a cause of acute colonic dilatation. Finally, we must remember that though their cases were clearly divided into patients with dysentery and patients with colitis, salmonella infection can arise in the clinical course of acute ulcerative colitis.5 Stool culture in the acutely ill patient with ulcerative colitis must be routine. An episode which threatens to go on to toxic dilatation may respond to non-operative management of such a superadded infection. LEPIDOPTERISM TEXTBOOKS of medical entomology are (quite rightly) mainly concerned with disease vectors. The directly harmful effects of arthropods are generally noted in a chapter on stinging and biting insects, spiders, scorpions, &c; and there is usually a small section on vesicant and urticating insects. The vesicant forms are mainly beetles, including the notorious "spanish fly" packed with cantharidin; but there are few of these and most of the trouble is urticaria due to various hairy caterpillars. These are not really dangerous; but, from time to time, they occur in vast numbers and physicians and entomologists are beset with complaints and inquiries. There have been several publications on the European species responsible and on the North and South American species; now there is a substantial account of the problem in the Australian region, by Dr R. Southcott, who has written a comprehensive review of the whole subject, including both entomological and medical aspects.1 It is not surprising that lepidopterous larvx have provided themselves with protection. Nearly all are thinskinned and juicy, offering tempting morsels to birds, insectivorous mammals, and lizards, as well as some arthropods. Some of them deter predators by being distasteful and toxic, often by concentrating components of their food plants (for example, cardiac glycosides’. 3. Goligher, J.C. Surgery of the Anus, Rectum and Colon.London, 1975. 4. Turnbull, R. B., Weakley, F. L., Hawk, W., et al. Surg Clins N Am 1970.
50, 1151. 5. Dronfield, M. W., Fletcher, J., Langhman, M J S. Br med. J 1974. i, 1. Southcott, R. V. Lepidopterism in the Australian Region. Records Adelaide
Children’s Hospital. 1978, 2, 89.
99.