496 



DISEASES OF THE SKIK 



For clearness of description it is indispensable to make a judicious 

 selection of them. 



Eczema, like any other inflammatory affection, shows different 

 stages of evolution. In our domestic animals it runs through the 

 phases of simple dermatitis in man ; thus, according to the nature 

 and aspect of cutaneous affections, we distinguish the following six 

 periods : 



1. Erythematous stage. Characterized at the beginning by hyper- 

 emia and a superficial exudation, it consequently results in the 

 thickeniDg of the epidermis, which disappears later through a pul- 

 taceous desquamation. The chronic condition of erythematous 

 eczema has received the name of squamous eczema; but most fre- 

 quently this is only the final stage of the eczematous process. Dis- 

 eases described by the following names are related to this type : 

 pityriasis, psoriasis, squamous herpes, mange, and also in the horse, 

 eczema of the canon and grease. 



2. The papular condition consists of small nodes which a micro- 

 scopic examination shows to be formed of a serous and cellular 

 infiltration and through the swelling of papillary elements. Papu- 

 lous eczema comprises lichen, rash (strophulus) and heat pimples of 

 the horse and ox. 



3. The vesicular condition. At times this is developed directly, 

 at other times it follows one of the preceding stages (when the 

 serous exudation is abundant in the papules and the cells of the 

 Malpighian layer are separated from one another, the liquid exu- 

 date reaches immediately the most superficial epidermic layer). It 

 represents in some ways the type of eczema; it is often desig- 

 nated simple eczema. It corresponds with herpes of our domestic 

 animals. Heat-rash of the horse may be related to it, but it has 

 nothing in common with the herpes of man. 



4. The moist condition (eczema madidans). It occurs after a 

 spontaneous or artificial opening of the vesicles (frictions); it is the 

 red eczema or moist rash. It is generally observed in the dog in 

 the shape of the rash or mange of obesity. 



5. The pustular condition. This is sometimes produced from the 

 outset, at other times it is due to the passage of vesicles into the 

 pustulous stage. After their opening the skin is often transformed 

 into a suppurating surface ; to a more or less considerable extent, it 

 is impetiginous eczema. It corresponds to pustulous rash, or to 

 scurvy eczema of the dog or horse. 



