333 



Technique. — Examine the blood of young calves, especially 

 those showing some emaciation. The blood is most readily 

 got from the ear. Wash the ear with a wet cloth, dry, and rub 

 until the veins become prominent, Wash stained films moment- 

 arily in acetic acid, i in 400 H.2O, otherwise the deep blue of 

 the red cells somewhat obscures the parasites. Examine very 

 carefully, as parasites may be scanty in chronic cases. 



The parasites are two to four m in length, one 

 to two M in widtli. Various forms occur in the 

 circulation — (i) a spherical or ovoid form, (ii) a 

 piriform parasite in pairs or fours. These are 

 characteristic, and give the name. Intermediate 

 stages between (i) and (ii) occur. The spherical 

 forms show a chromatic particle, and closely 

 resemble ' young rings.' The chromatic body 

 (nucleus) divides into two portions, one going to 

 each end ; the parasite elongates, and by this means 

 the piriform body is got. The piriform parasites 

 are two to three m long and about one m in 

 diameter. 



(iii) Bacillary forms showing, however, a red 

 chromatic spot and blue protoplasm (Fig. 75). 



(iv) Large double forms having a curious 

 resistent appearance [Vide Plate) probably gamete 

 forms of P. bovis. 



The number of parasites in the peripheral 

 circulation is proportionate to the severity of the 

 disease — one to two per cent, of corpuscles are in- 

 fected, at the end of the disease five to ten per 

 cent, (or even twenty-five to thirty per cent.) The 

 number in the blood is not so great as the number 

 in the spleen (ten per cent.), Hver (thirty per cent.), 

 and especially kidneys (eighty per cent.) 



Free parasites are found in the blood in the 



