Relation of number of parasites to severity of infection Other aids to diagnosis Absence of malarial parasites in kala-azar cases 136 -, REMARKS ON KALA-AZAR No cases that presented only atypical bodies were included in the list of those definitely diagnosed, though it is a striking fact that these bodies were only found in those with typical parasites, or in cases that were clinically kala-azar. These atypical bodies are illustrated in Plate VIII., figs. 7, 8, 9, 15 and 16, while others were frequently seen having no signs of a blepharoplast.

In ten cases the parasites were readily found, and the diagnosis settled by a few minutes microscopic work, but the remaining twelve needed much laborious work before they could be demonstrated.

Major Cummins, R.A.M.C., stated that the number of parasites found had no relation to the severity of the infection. My experience certainly does not coincide with his, for my cases, which were acutely ill with the disease, practically invariably presented a large number of parasites in the splenic films, and only required a few minutes for microscopic diagnosis, provided that true splenic blood was withdrawn. In contrast to this, the chronic cases presenting wasting, prominent abdomens, large livers and spleens, and a low fever, and which could easily be diagnosed on clinical grounds alone, presented very few parasites, and often it was extremely tedious to demonstrate them, while in several such cases there was an absolute failure. I do not think any of these were chronic malarial cases.

Fifty-six splenic punctures were performed during this tour, and twenty-two positive results were obtained. In thirty-nine cases, which were undoubtedly kala-azar from a clinical standpoint, nineteen showed parasites in their splenic blood—/.e. in about 48°5 per cent. of the clinical cases the parasite was demonstrated.

Other aids to diagnosis, such as the type of fever, the effect of quinine, leucopenia and differential counts, could seldom be employed, owing to the impossibility of following up the cases and to lack of time.

Though a differential count is most useful when one has a patient under constant observation, yet for such a rapid tour of investigation the method was found by me of little value, the percentages varying considerably. Without finding the parasite I felt that a diagnosis, founded on not very definite clinical grounds, together with a differential count supposed to indicate the presence of the disease, was scarcely sufficient to justify isolation and destruction of property.

In the definite kala-azar cases the finely granular polymorphonuclear leucocytes were usually present in numbers varying from 30-45 per cent., while the large mononuclears varied from 16-32 per cent.

Malarial parasites were not found in a single case of kala-azar, either in the peripheral or splenic blood, and in the suspected cases only in four instances.

Considering how extremely common malaria is, this is very remarkable, and I can only suggest that it is a case of the survival of the fittest. The weaklings dying off from malaria in early childhood, those with stronger constitutions surviving and growing up, gain an immunity, so that, although suffering from malaria during the rainy season, yet they are capable of ridding their general circulation of the parasites when once the malarial season is over, in spite of their not taking quinine. This tour was made during the non-malarial season.

In several cases the peripheral blood was watery and spread on the slides extremely badly. In three virulent cases it resembled cloudy serum.

The type of parasite usually encountered was the typical one now so well known as to need no description, Plate VIII., fig. 1. Most of the forms were free and well developed.