648 11. M. WOODCOCK. 



receptacle, and at once defibrinated. As before, equal 

 volumes of blood and agar are mixed. The tubes, when 

 prepared, must be sterilised by the fractional method at a 

 temperature of about 100° C. (under rather than over), for 

 an hour or so on two successive days. This is necessary to 

 ensure sterility. 



Owing to this process, however, tub.es prepared thus are 

 often deficient in expression-liquid ; to remedy this 1 or 2 c.c. 

 of boiling salt-citrate solution ('75 per cent, salt + 1 per cent, 

 sodium-citrate), are added to each tube, which is then left 

 for a day or two before being inoculated; the liquid absorbs 

 nutrient material from the solidified part. The trypanosomes 

 Avill not live in salt-citrate solutions alone. I have tried various 

 combinations of salt, sodium-citrate, and (or) citric acid, 

 similar to those used in cultivating the Leish man-Donovan 

 bodies, but with no success. For the practical purpose of 

 ascertaining whether a bird is infected or not I have found 

 these tubes to be, as a rule, as serviceable as the others; 

 but I do not think they suit the parasites quite so well. 

 The culture does not start quite as easily, and multiplication 

 is often somewhat slow at first. It is at least four or five 

 days before the trypanosomes can be found at all readily in a 

 small drop taken for examination, whereas in the case of the 

 other tubes thi-ee or four days usually suflBce. Again, after 

 a week or nine days the parasites tend to become very 

 granular and altered, and large agglomeration-clusters form 

 sooner. In short, the trypanosomes do not live " healthily ^' 

 so long in this kind of culture as in the other. 



I may point out, with regard to the macroscopic appearance 

 of infected tubes, that in the case of the pai-asites with 

 which I have been- working, there is normally nothing 

 indicative of their presence to be seen. A culture (if free 

 from bacteria) looks just like an uninoculated tube. Even 

 when the pai'asites are very abundant, the expression-liquid 

 remains clear and unaltered in colour. Not once have I 

 found the parasites on the solid part of the medium. They 

 never form visible colonies or masses there. The only 



