386 RESEARCH IN PROTOZOOLOGY 



canary is virtually certain to show an acute infection within from 

 two weeks to a month, dej>ending on the species of Plasmodium 

 concerned. Since the number of parasites is small during the 

 chronic stage of the disease the length of the prepatent period in 

 birds inoculated from latent cases will usually exceed the figures 

 given above, although its blood should be examined for parasites 

 four or five days after the initial inoculation and thereafter until 

 they are found. 



II. MetJiod of transferring infection. The technique of trans- 

 ferring the infection is as follows : the large vein on the inside 

 of the tarso-metatarsus is punctured with a small Hagedorn needle 

 and the blood so obtained is sucked up into a small Luer syringe 

 into which 50 or 100 cubic millimeters of citrated salt solution 

 has previously been placed. (A solution containing two per 

 cent sodium citrate and 0.7 % sodium chloride has been found 

 very satisfactory for this purpose by the author. Physiological 

 saline also works quite well but is less efifective in preventing clot- 

 ting.) When the requisite amount of blood has been obtained it 

 is injected into a clean bird. It is usually found most convenient 

 to inject the breast muscle, since there are no feathers in this 

 region and those which are on the sides can easily be brushed 

 away with a piece of cotton soaked in seventy per cent alcohol. 

 A second advantage of inoculation at this point is the fact that 

 there is usually little bleeding. If desired, intraperitoneal inocula- 

 tion can be employed. There is less bleeding with this method 

 than with any other, and with a little practice the technique is 

 easily learned. Intravenous inoculation can be accomplished by 

 using a No. 27 (or better, a No. 28 Luer needle. If the needle has 

 been slightly bent by heating in a micro-burner, injection can be 

 more easily made and there will be less danger of tearing the 

 wall of the vein. The leg vein already referred to is the most con- 

 venient site for this type of inoculation, and will be found quite 

 large in older birds. Intravenous injection will be found easier if 

 the bird is first wrapped in a piece of cloth, in which holes have 

 been left for the legs. The bird can then be placed on a table, 

 with a small bit of cotton under the leg into which injection is 

 to be made, and while the leg is held rigid with one hand the 

 syringe is held in the other and the solution is forced into the 

 vein very slowly. The process may be found somewhat easier if 

 an assistant is on hand to hold the bird. Care must be used in 



