DISEASES OF THE POLL. 781 



considered to be so many active agencies in the etiology of poll 

 evil. 



In cattle it is most commonly chargeable to the pressure and 

 frictions of the yoke. Hertwig, with other German authors, con- 

 siders it, and particularly the sus-atloid hygroma, as the local mani- 

 festation of a diathesic condition, such as rheumatism and dis- 

 temper. They also admit that the true poll evil may develop itself 

 spontaneously, and independently of all other traumatic causes. 



In considering the various forms which the disease may assume 

 in this locality we shall adopt the division sanctioned by Bouley, 

 who has thus arranged them. 



A — ExcoKiATioNS ; B — (Edematous Swellings; C — Cobe; 

 D — Bloody Tumors. 



Diseases of the poD, in horses, exhibit too close a resemblance 

 in their type and general history to escape notice, and the ther- 

 apeutic indications exhibited in them are the same. And it must 

 be borne in mind that however slight they may ajDpear to be, and 

 whatever may be their nature, they always require immediate at- 

 tention and careful watching, and in all cases the use of the bridle 

 and the halter must be suspended. 



E.— Cyst. 



Cysts of the poll are divided into superficial and deej). The 

 former, which are of uncommon occurrence, have their seat in the 

 subcutaneous cellular tissue, and possess features in common with 

 those which appear at the withers. The latter is an abnormal 

 dilatation of the serous sac which facHitates the gliding of the 

 cervical cord upon the atlas ; it is also known as the atloid hy- 

 groma. It generally begins suddenly, and is manifested by the 

 presence of a soft tumor, fluctuating, spherical, or bilobulated by 

 the median pressure of the cervical ligament. It is usually pain- 

 less, except when it is the result of acute \iolence, in which case 

 it may be accompanied with inflammatory symptoms, which may 

 extend to suppuration, but in such cases, which, however, are in- 

 frequent, there is also a degree of fever corresponding in intensity 

 with the other features of the case. The fluctuation is at first 

 imiform, and easily detected, but at a later period, as the secre- 

 tion becomes more abundant, and the tension of the pouch be- 



