DESICCATION AND DESQUAMATION. 81 



matory action \vliich existed in the dermis, and is 

 always protracted when suppuration has taken place. 



The crusts vary from a brownish yellow to a black 

 colour ; they likewise differ in thickness, being of 

 greater substance when cast off from a pustule than 

 when ft-om a vesicle : a fact which is referrible to the 

 dried pus being united mth the desquamated cuticle. 

 The crustaceous stage is accompanied with a subsidence 

 of the eruption ; but many of the papula3 will be found 

 vesicated when scabs are forming on others ; and some 

 of them will have pale yellow crusts on their surfaces, 

 produced by simple desquamation of the epidermis in 

 the form of furfuraceous scales ; in such instances, as 

 no vesicles are developed, the skin soon regains its 

 normal condition. 



The fall of the purulent scabs leaves pits of various 

 sizes on the site of the original papulae : the depth of 

 these, and the time occupied in the process of cicatri- 

 zation, are necessarily proportionate to the extent of 

 the ulceration. 



The gi'eat liability of the vesicles to receive injury, 

 and of the crusts to be forcibly detached by the sheep 

 scratching and iTibbing themselves, interferes consider- 

 ably both with the regularity of the progi^ess and the 

 local symptoms of the disease. Hence, when the erup- 

 tion breaks out on the face, two or three weeks usually 

 elapse before the healing of the sores is completed. The 

 Frontispiece to this work gives a good representation of 

 the production of scabs, as modified by the injuries 

 alluded to. — See plate. 



From the account here given of the several stages 

 of ovine variola, it will be seen that considerable ir- 

 regularity exists in its development, and also in the 



M 



