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176 Morbid anatomy (Fig. 49).—— No gross lesions of the nerve centres, or of any other organ, have been described as invariably present; but in every case indications, principally microscopical, of an extensive meningo - encephalitis can be demonstrated. In a proportion of instances congestion of the meninges, effusion of lymph, increase and turbidity of cerebrospinal fluid, are found. In all cases, as first pointed out by Mott, there is an extensive small-cell infiltration of the perivascular lymphatic tissue throughout the brain, cord, and meninges, varying in amount in different cases and in different anatomical regions. This, the essential pathological feature of sleeping sickness, recalls the very similar condition in general paralysis of the insane. The nervous elements exhibit secondary degeneration changes.

Similar changes are described by Mott in the nervous system in dourine, and chronic trypanosomiasis in the monkey. Mott has also pointed out that the lymphatic tissues throughout the body are similarly affected. Bettencourt and other Portuguese observers, as well as Castellani, have described a diplococcus in the brain in sleeping sickness. This organism is in no sense causally related to the disease; it must be regarded merely as a terminal and non-essential epiphenomenon. Similarly, Filaria perstans (which at one time, in consequence of considerations of frequency of concurrence and geographical distribution, was regarded as being possibly the cause of the disease), the various intestinal worms, and Schistosomum hœmatobium, though often met with in sleeping sickness, are present only as accidental concurrences. Diagnosis.—— Chronic irregular fever, more especially if associated with enlarged cervical glands and, in the European, erythema multiforme, in a patient who has resided in tropical Africa at any time during the previous seven years, but more especially recently, suggests a tentative diagnosis of trypanosomiasis and detailed examination with this possibility in view. Diseases with which trypanosomiasis might be confounded are malaria, kala-azar, pellagra, syphilis, leprosy, and, in its later stages, beriberi,