G. H. F. Nuttall and G. S. Graham-Smith 257 
Journ. Hygiene, vi. p. 642) advanced the hypothesis that P. bovis 
undergoes development into a trypanosome, a statement which has gained 
no support from subsequent investigations. Should Theileria develop 
into a trypanosome we would have an additional gi'ound for separating 
it, in the light of our present knowledge, from Piroplasma. 
2. Blood-platelets and kaematozoa. 
In connection with these cultivation experiments Swingle’s (1908) 
observations on the similarity between blood-platelets and certain 
haematozoa are of interest. He made cultures of normal sheep 
and other blood in a medium of the following composition: water 
1000 c.c., sodium citrate 5 grms., sodium chloride 5 grms. made slightly 
acid with hydrochloric acid. One drop of fresh blood was added to 
2 c.c. of the solution. For making stained preparations he placed a 
drop of the culture fluid on a slide and after it had evaporated down, 
but was not entirely dry, he dropped on some killing fluid such as 
Zenker’s solution. The specimens were stained by various methods. 
He remarks that “ normal platelets resemble normal piroplasma 
forms in size and general shape. A nucleus, and refractive spots, 
probably vacuoles, can be seen ” (p. 49). We cannot entirely agree 
with this statement, since in our own preparations we have seldom 
found any difficulty in distinguishing between blood-platelets and forms 
of the parasite. 
Swingle’s observations, which are quoted at length, on the cultiva¬ 
tion forms of platelets are extremely interesting. “ Cultures examined 
as quickly as possible after drawing the blood showed amoeboid and 
flagellate forms. A fact of great importance to the student of 
haematozoa is that the most of these forms are capable of movement. 
They seem to roll over, swing round, and often move for a distance 
equal to the diameter of two or three red corpuscles. Among the 
amoeboid types there were always present in great numbers platelets 
with few or several long, sharp, or sometimes blunt, pseudopodia. From 
the description and figures of Koch and Ivleine one must conclude that 
these forms are very similar to, if not identical with, what they describe 
as developmental stages of Piroplasma. To be sure Koch found his 
stages in the stomach of the tick, but this does not disprove the state¬ 
ment, for just such forms were also found in the stomach of the sheep 
tick after sucking the blood of a sheep....In older cultures most of the 
platelets that had no pseudopodia were at the rim, either inside or just 
