SEROLOGICAL ^lETHODS IN THE STUDY OF PROTOZOA 425 



an increase of euglobulin in the serum. (See Brahmachari, 1917 

 and 1923; Napier, 1922; Ray, 1924 and 1927.) 



The tests are extremely simple to perform. Thus, in Brah- 

 machari and Sen's (1923) modification of Brahmachari's test, 

 serum is mixed with six times its volume of distilled water and 

 poured into a graduated cylinder until some black spots (previously 

 fixed at the bottom) are just visible. The height in inches varies 

 inversely with the amount of precipitate and a reading of 1.25 

 inches or less is regarded as positive. In Napier's aldehyde test, 

 one drop of commercial formalin (thirty per cent formaldehyde) 

 is added to one cubic centimeter of serum ; the mixture is shaken 

 and put at room temperature. Kala-azar serum will set and become 

 opaque in from three minutes to twenty- four hours. 



SEROLOGICAL INVESTIGATIONS AMONG THE PROTOZOA : RESULTS AND 

 SPECIAL TECHNIQUES 



A. Amccbiasis. The serology of amoebiasis will not be con- 

 sidered because it is taken up in detail by Dr. C. F. Craig in 

 another chapter of this book. 



B. Leishmaniasis. Most of the work on leishmaniasis has been 

 done with kala-azar and available data indicate that in this disease 

 antibodies are difficult to demonstrate, appear very variably, and, 

 so far, offer little promise of perfecting standardized diagnostic 

 tests. Since killed cultures of L. donovani stimulate the production 

 of antibodies of high titre when injected into man or animals, 

 since the serums from recovered cases of the disease apparently 

 manifest high titres and since kala-azar is essentially an infection 

 of the reticulo-endothelial system which is probably most active 

 in the production of antibodies, the lack of high titre in this 

 disease may be due to a blockade of the reticulo-endothelial sys- 

 tem by the parasites. In complement fixation, many investigators 

 have used extracts of infected spleens (see especially di Cristina 

 and Caronia, 1913, and Hindle, Hou and Patton, 1926) ; others 

 have used cultural flagellates (Auricchio, 1927). The agglutina- 

 tion studies have been done with suspensions of cultural flagellates. 



In marked contrast to the specific serological antibodies, very 

 promising results have been obtained in kala-azar with the mis- 

 cellaneous tests. Tables 7 and 8 are representative of the many 

 papers on these tests. The data given by Napier (1923) in Table 

 7 show the correspondence between the aldehyde test and the 



