ECZEMA IN THE DOG. 28 1 



Heredity exercises an unquestionable influence. It depends on the 

 transmission of a tendency to changes in the bodily fluids, or to general 

 nutritive disturbance. 



Bacteriology had scarcely been raised to the rank of a science 

 before at-tempts were made to found a parasitic theory of eczema. 

 Eczematous patches exhibit a complex flora of micrococci and 

 bacteria, whose rule in the pathogen}- of outbreaks is still undeter- 

 mined. In point of fact, organisms may be found as abundantl}-, and 

 in as great variety, on the healthy skin of neighbouring parts. Never- 

 theless the microbes which multiply on eczematous spots are not 

 without influence on the course and changes of the disease. They 

 aggravate acute eczema, and parth' contribute to the obstinacy of 

 chronic forms. Nowadays the tendency appears to be in favour of 

 admitting that human vesicular eczema results from the action of 

 various cocci which occur massed in twos, fours, or larger numbers, 

 and which either occupy the intercellular spaces, or are included 

 within the cells forming the vesicle ; to these Unna has given the name 

 of morococci. In impetigo, a disease now regarded as contagious and 

 inoculable, pyogenic microbes, especially the Staphylococcus pyogenes 

 alhus and aureus, appear to be the true agents of transmission. 

 Whether it succeed to certain suppurating skin lesions or originate in 

 trifling superficial solutions of continuity in the skin, this form essen- 

 tially consists in infection of the papillary layer, and is characterised by 

 pustulation, followed by more abundant secretion than that of- ordinary 

 eczema. But further research is necessary to determine the part 

 played by microbes in the pathogeny of eczema. 



The chief causes of eczematous disease in the dog are cutaneous 

 irritation, disturbed nutrition, improper feeding, and abnormal condi- 

 tions of life. ^Etiologicall}' these skin diseases may be divided into 

 two groups, under the titles of essential and symptomatic eczema. 

 Essential eczema is directly induced by external irritation of any 

 given portion of the skin. In dogs with fine skin it may be caused by 

 mechanical, thermic, or chemical agencies ; by rubbing or repeated 

 pressure ; by solar irritation ; and by the action on the skin of an}- 

 of a large number of topical irritants. It soon disappears, w-ithout 

 spreading. It appears to have no hold on the organism, and does not 

 return unless the causes which have produced it are repeated. 



The pathogeny of symptomatic eczema is dominated by some 

 internal causes, either of constitutional, alimentary, or nervous origin. 

 Various changes in the body fluids resulting from previous morbid 

 conditions, or from mal-assimilation, may produce it. Sometimes 

 these internal influences are alone the cause ; sometimes, while giving 



