706 . MISS ANNIE PORTER ON A [June 16^ 



tubules, salivary glands, reproductive organs, and body-cavity of 

 the lice. Smears of these organs, fixed wet with osmic vapour,, 

 were afterwards stained and examined microscopically, but fresh 

 preparations in normal saline to which a little methylene-blue had 

 been added, were also examined in this case. 



(b) Fixed inaterial. 



The blood smears were usiially fixed wet with osmic vapour or 

 with osmic vapour and alcohol. Occasionally they were allowed 

 to dry quickly and afterwards treated with methyl alcohol before 

 staining. The chief stains used were Giemsa's mixture of azur ii. 

 and eosin, Loeffler's alkaline methylene-blue, and Delafield's 

 haematoxylin, the latter used alone or sometimes followed by 

 safranin. Azur ii. followed by lichtgrlin was tried occasionally,. 

 and safranin alone — suggested by the presence of a refractile cyst- 

 like envelope round some of the parasites — was tried, but found 

 to be too transparent and difi"use. The best results were obtained 

 with Giemsa's stain, alkaline methylene-blvie, and hsematoxylin. 

 The same stains were used for the organ smears of lice. 



The preparations were usually mounted in Canada balsam,, 

 sometimes left uncovered. 



The various methods outlined above were tried for the purpose 

 of correlation and corroboration, and to eliminate possible errors. 



Y. General Structure. 



The general shape of this parasite, which occurs either inside a 

 leucocyte or free in the blood-plasma, may be desci-ibed as vermi- 

 form or gregariniform, in fact, that of a vermicule (PI. XXXIX. 

 figs. 1, 2). However, there is very often no marked difference 

 between the ends, which are then somewhat I'ounded ; and 

 further, as some of the parasites are comparatively broad for 

 their length, they may be quite accurately described as bean- 

 shaped or reniform. The size varied from 17/i to 7^ in length 

 and 5-9;l( to 4^ in breadth. 



The free parasites, averaging 10"9/x long by 5*1^ broad, are 

 usually surrounded by a cytocyst which is very refractile and 

 does not stain at all easily (PL XXXIX. fig. 8). Their cytoplasm 

 is rich in granules which react vigorously toward stains and 

 thereby obscure the oval nucleus lying beneath them. The 

 distribution of the granules varies, and this accounts for the 

 differences in the nuclear apparatus as seen in the figures. The 

 nucleus is generally nearer one end in position. 



Differences between the ends of the organism occur in cytozoic 

 forms. One end may be larger than the other. This may be 

 the natural result of the cytozoic habit, the organism assuming 

 the form most suitable to a limited space, or it may be due to the 

 twisting of the body on itself and within the spherical leucocyte, 

 which results in the "thin edge" or "tailed" appearance of 

 some of the parasites (text-fig. 154 D-'K). U-shaped forms as 



