1912.] The Development of a Leucocytozoon of Guinea- Pigs. 71. 



jelly method, because, probably, they stain momentarily as the trypanosomes 

 do, and immediately die and become achromatic, and unless stained they 

 are not visible. By the examination of ordinary wet films of the blood 

 I was unable to demonstrate the presence of these free flagella, although a 

 disturbance of the corpuscles was frequently seen. But the blood of some 

 infected guinea-pigs, drawn under all aseptic precautions and examined by 

 the dark ground illumination, showed free-swimming spirochaste-like bodies. 

 It was not until the blood of highly infected guinea-pigs containing full 

 matured lymphocytozoa was treated with an equal part of a 1-per-cent. 

 solution of " globin "* and incubated at 37° C. for eight hours that the free 

 flagellate forms in the blood plasma could be fixed and stained by ordinary 

 methods (fig. 18). Even by this process it is not always possible to demon- 

 strate them, and the maceration involved gives them the appearance of spirilla 

 with blunt ends. However, some of the spirilla obtained after the treatment 

 with the " globin " show the wavy outline of spirochsetes. Sir Bonald Boss 

 was the first to suggest that these flagellate forms constitute the gametes 

 of the parasite ; this seems quite probable, though no separate female form 

 has yet been noticed. It will be remembered that Lewis suggested that 

 trypanosomes are sperms, and, perhaps, these spirochsete-like bodies are 

 similar stages of a larger parasite. 



What may possibly be the last phase of this parasite has occasionally been 

 seen in preparations which had been submitted to the action of " globin " 

 for a further period of four hours. It is an object which resembles some- 

 what the trypanosome " latent bodies " described by Moore and Breinl 

 (fig. 19). Hunter has also mentioned the presence of amoeboid forms of this 

 parasite being free in the plasma, but he does not picture them. These may 

 be the form now drawn (fig. 19). 



Dr. J. W. Cropper and I have repeated and can confirm the experiments 

 of Ledingham (1906) and Hunter (1909), namely, that newly-born guinea- 

 pigs do not show these lymphocytozoa in their blood. Although a pregnant 

 animal may be markedly infected, the young, when born, possess no parasites. 

 As has been already observed by these writers and by Schilling (1911), the 

 number of parasites found in both the peripheral blood and in that of the 

 internal organs of any one infected guinea-pig varies greatly from day to day. 

 The parasites seem to appear in large numbers, to diminish, to disappear, and 

 then, after a varying period of time, to reappear. Except for a slight ansemia, 

 shown by the presence of an increased number of erythroblasts in the peri- 

 pheral blood, the guinea-pigs do not suffer apparently. The livers of many 



* The filtrate of a solution of lisemoglobin which has been precipitated by heat 

 H. C. Koss claims that this substance induces the division of certain cells. 



