ABERRATION OF THE APPETITE. 



55 



Licking-disease is a special morbid condition, the principal 

 symptom of which is an irresistible desire felt by the animals to 

 lick, chew, and swallow if possible, the most diverse and most 

 disgusting objects. The disease assumes a chronic course ; it 

 finally produces digestive and nutritive troubles, leading to 

 cachexia and death. Concerning its frequency among our dif- 

 ferent domestic animals, these must be classified in the following 

 order : ox, pig, horse, and goat. 



Etiolog-y and Pathology. The licking-disease constitutes a 

 symptomatic morbid type rather than a pathological change, and 

 the manifestation which generally dominates its clinical picture 

 is common to numerous aifections. Its nature has, for this reason, 

 been very differently regarded. It has been ascribed to infection, 

 to heredity, and to imitation; some authors have made of it a nervous 

 disease, while others have traced it to osteomalacia ; others again 

 have ascribed it to local defects, to improper alimentation, and to 

 the particular constitution of the soil. 



1. Infection and heredity have been considered as being the 

 cause of the disease from the earliest times, but without any suffi- 

 cient reason, as a close observation of facts testifies. 



2. If imitation is sometimes the cause of a condition similar to 

 the affection which we are now considering, it is not to be ad- 

 mitted as being able to produce the true pica disease in the proper 

 sense, this trouble corresponding to a profound alteration of nutri- 

 tion. Indeed, Lemke's experiences are absolutely demonstrative 

 in this respect. 



3. Tscheulin considers the disease as a depravity of the sense 

 of taste, and describes it under nervous diseases. According to 

 Spinola and a few others, its immediate cause is probably an alter- 

 ation of the sensitive nerves of the stomach, and a kind of func- 

 tional trouble of the pneumogastric. Quite recently, Lemke has 

 defined it as ^' a chronic disease consisting of a perversion of nu- 

 trition, produced by a lack of phosphorus, and which starts as an 

 affection of the central organs and nerves taking a leading part in 

 nutrition.^' No one will contest the participation of the nervous 

 system and the complex symptomatic apparatus of the disease ; 

 the function of the nerves of the palate appear to be particularly 

 affected ; but it is by no means proven that the nervous symptoms 

 are always primary, and that licking is a symptom connected 

 with this affection in all cases. Haubner and Siedamgrotzky are 



