442 DISEASES OF THE SKIN 



that the glands and canal of exit are filled with purulent or bloody matter. 

 Soon the internal follicles become involved; the masses of matter can be 

 easily pressed out of the orifice of the follicle, and we may have an elas- 

 ticity of the purulent cavity surrounded by infiltrated cutis in which we 

 find the hair has become entirely detached from the follicle and falls out. 

 This condition is generally a rather serious affection in the dog, as in this 

 animal there are always several follicles which are accumulated into 

 one group with a common orifice, and in every case of cutaneous disease 

 we find a group of affected sebaceous glands. 



In very bad cases peri-glandular and peri-follicular inflammation 

 may become so acute that we see the formation of an extended nodule- 

 shaped, dark red swelling, forming a so-called "boil." This is marked 

 after a certain period by a yellowish-green, necrotic thrombus, which 

 becomes detached by purulent disintegration of the surrounding tissue, 

 and is sloughed after the pus has been discharged. In such cases we 

 find that not only is the external surface of the skin impaired, but the 

 corium is affected, and as the follicles are destroyed the hair does not 

 return. The formation of abscesses and ulcerations, also inflammations 

 of the skin, will be discussed further on. 



In chronic cutaneous inflammation we may see the formation of 

 hypertrophic as well as atrophic conditions. In the former case we find 

 as a consequence of the constant increase and congestion of blood in the 

 part the formation of sui^erfluous connective tissue, whereby the skin 

 may be thickened several times its normal size and may form large folds 

 or collosities, and in rare cases club-shaped or warty elevations. In the 

 latter case the corium becomes thinner. This is also the case with the 

 epidermis. Its tissue is either greatly reduced or greatly increased in 

 size, and in the latter case the epidermic cells which proceed from the 

 deep part of the tissues do not undergo any horny degeneration, but 

 rather a drying, mummifying process, covering the membrane in the 

 shape of numerous whitish or white-gray scabs. 



NON-PARASITIC DISEASES OF THE SKIN. 



Erythema. 



{Redness of the Skin.) 



Erythema, due to disorders of the circulation, is the mildest form 

 of inflammation of the cutaneous membrane and consists either of 

 normal hypera>mia of the corium in its upper layers (erythema simplex, 

 erythema congestivum) , or it may be due to a slight sero-cellular infiltra- 

 tion of the membrane of Malpighi — erythema exudativa (dermatitis 

 erythematosa). 



