GENUS: TEYPANOSOMA 459 



development in the vertebrate. It may be a form of T. evansi modified 

 by long passage from vertebrate to vertebrate without an arthropod 

 intermediary. 



CURATIVE ACTION OF DRUGS AND SERA IN TRYPANOSOMIASIS. 



The serum of certain normal animals when injected into rats or other 

 laboratory animals infected with pathogenic trypanosomes will sometimes 

 cause their temporary disappearance. For instance, a dose of 0-1 to 

 1 c.c. of human serum injected into a mouse infected with T. brucei 

 may cause the trypanosomes to disappear entirely from the blood. Some 

 strains of T. brucei resist such treatment, as also does the human strain 

 (T. rhodesiense). The serum from animals, such as the goat, which have 

 recovered from an infection is little more active than a normal serum, 

 so that at present there seems little possibility of a serum therapy in 

 trypanosomiasis being devised. 



Much more definite results have been obtained with chemical agents. 

 Ehrlich and Shiga (1904) gave an account of the action of the organic dye 

 trypanrot on trypanosomes. They showed that a fair proportion of 

 experimentally infected animals could be permanently cured by its 

 means. A long series of investigations on allied organic compounds was 

 carried out by Nicolle and Mesnil (1906), and it was found that a definite 

 relationship existed between the structure of the molecule and the thera- 

 peutic action. 



Thomas (1905) announced the fact that the organic arsenic compound 

 atoxyl had a specific action on trypanosomes, and was very much less 

 toxic than arsenious acid, which had previously been employed in the 

 treatment of sleeping sickness. The introduction of atoxyl led to a 

 series of investigations under the direction of Ehrlich, which resulted in 

 the elucidation of the chemical nature of atoxyl and the preparation of 

 other organic arsenic compounds, notably arsenophenylglycine, and 

 finally salvarsan. Many other allied drugs were produced, and it is 

 chiefly in one or other of these forms that arsenic is now employed in the 

 treatment of trypanosomiasis. 



Antimony in the form of sodium or potassium antimony tartarate 

 (tartar emetic) has a marked action on trypanosomes, which disappear 

 rapidly from the blood of animals after intravenous injection. As they 

 disappear the trypanosomes show evident signs of degeneration, while 

 smears from the spleen show quantities of debris from the broken-down 

 organisms. Though the trypanosomes may disappear entirely from the 

 blood after a single injection, they almost invariably reappear after a 

 number of days. It seems apparent that it is rarely possible to give at a 



