aO DEPARTMENT OF AGRICULTURE 



seconds and carefully dry between blotting paper. The addition of the water to the 

 stain on the slide is a very important matter, for, if it is not quickly and evenly 

 performed one portion may be lightly and another deeply stained. The examination 

 of the stained blood smear may be made with a dry or oil immersion lens. Personally 

 a 4.0nmi Zeiss objective with a No. 4 compensating eyepiece is preferred. 



Through the use of the foregoing staining material we have been able to secure 

 more uniform results than were possible prior to its adoption. Further, we are able 

 to modify the stain to suit the requirements of any special work in hand and modifi- 

 cations have been found necessary when the stain is used on smears taken from the . 

 vagina, especially after an irrigation with citrate solution in a search for trypanoao- 

 mata. 



To those familiar with the ordinary materials and their use- in connection with 

 films of human, guineapig or rabbit blood, the need for a material which will give 

 equal results when horses' blood is to be stained is not appreciated. We have found 

 horses' blood much more difficult to stain than the blood of any of the other animals 

 either wild or domestic, which we have had occasion to examine. Watson has been 

 able to secure some remarkably uniform results with this stain in his studies of the 

 Trypanosoma equiperdttm at the Lethbridge quanantine station. 



Apart from the difficulties of staining we have also found other problems which 

 need further elucidation in connection with blood work. One of the most important 

 is the number of cells it is necessary to count that a fair average result may be 

 obtained. To indicate our efforts in this direction I api>end hereto a table (table I) 

 which gives the counts made on three different smears taken from the same animal 

 at the same tim^. A careful study of this table reveals that the smaller the number 

 of cells counted, the greater is the possibility of error, and while four hundred cells 

 may indicate a percentage very near to the average, five hundred may give a per cent- 

 age which i.s far from the average. As a rule, however, the counting of one thous- 

 and cells on a single smear will give an average very similar to the average of a 

 larger number. Whenever circumstances have permitted, we have counted one 

 thousand cells, curtailing the number enumerated when the smear and the laboratory 

 conditions did not admit of a longer search. 



Tables II., III. and IV., give the results of counts made of the blood of horses 

 affected with dourine. The two former tables are made up from data obtained in 

 connection with the chronic affection (see also Chart I. and II.), while the latter 

 (Table IV.) refers to data obtained from an acute case of dourine. 



Table V. gives the counts which we obtained from the blcod of a stallion (650), 

 already referred to as being used in our breeding experiments. (See also Chart 

 III.) This stallion has presented nothing out of the ordinary in his general clinical 

 appearance, although he was used on the mare (589) during the season of 1906, on 

 various occasions. There has never been any clinical manifestation indicating a 

 dourine infection, and the knowledge of systematic examination of horses' blood is 

 so limited that we are unable in this particular instance to explain the marked 

 variations which occurred in the differential counts on various occasions. 



The stallion 660, a record of whose blood-counts, appears in Table VI., was, as 

 has already been mentioned, known to be suffering from a parasitic invasion, of the 

 blood, merely from the results of the differential blood-counts made at the time of 

 his purchase. This marked eosinophilia was very interesting. This horse was used 

 for service with the mare 588, but did not develop any symptoms indicative of a 

 dourine infection, nor did this mare subsequently present any evidence of being with 

 foal. A reference to the autopsy findings in this case reveals the correctness of the 

 diagnosis made months before his death. 



Table VII. presents a few counts made of the blood of the mare (670), used in 

 our breeding experiments with the stallion (650). This mare has not given any 

 evidence of a dourine infection up to the present time, nor has it been possible to 

 get her with foal. 



