1912.] On the Extrusion of Granules by Trypanosomes. 389 



No. II. 



November 5. — Gerbil (F. 11) injected with blood (0 - 2 c.c.) obtained as above, but after 

 two hours' standing no trypanosome could be seen, only round forms and free granules. 

 November 12. — Trypanosomes first found in blood. 

 November 14. — Trypanosomes very numerous. 

 November 15. — Gerbil found dead ; spleen very large. 



The average time of infection in gerbils is four to six days after ordinary 

 inoculation. Similar results were also obtained with dogs. 



These experiments are, of course, not absolutely conclusive, but so far as 

 could be ascertained microscopically the granules were the only discernible 

 remnants of the trypanosomes which retained their characteristic form. 



Further experiments were also made to trace if possible the fate of 

 granules so injected into animals. Inoculations were made with solutions 

 containing large number of free granules, and the animals were killed before 

 trypanosomes could be found in the blood. Granules and the later forms in 

 various stages of development were found in the proximal glands, also in the 

 internal organs. 



Note on a Nev; Method of Blood Fixation. 



By H. G. Plimmee, F.E.S. 



During some years of work on the blood of animals, many methods of 

 fixation have been tried, principally with the view of obtaining a better 

 fixation of blood parasites. The method described below has fulfilled this 

 object better than any other, and is more faithful than even osmic acid. 



The use of iodine for the fixation of unicellular organisms dates from the 

 work of Kent in 1881 on the Infusoria, but the application of it to blood is, so 

 far as I know, new. 



I have used iodine in two forms, in vapour and in solution, and each has 

 its special advantages. When a blood-film is exposed wet to the vapour 

 from a solution of iodine in chloroform, the fixation of the various elements 

 is practically instantaneous, as the penetrative power of iodine in this 

 form is greater than that of any other fixative known to me ; there is less 

 alteration both in form and size of the cellular elements and parasites than 

 with any other fixative. When used in solution several things happen which 

 are of value in enabling very fine structures to be more easily made out. 



If blood be mixed with a solution of iodine in salt solution containing iodide 

 of potassium, certain elements and parasites, especially trypanosomes, swell 

 up so that the finer parts of their structure, for instance the nucleus and 

 blepharoplast, are much clearer and more definite than with the ordinary 



