'58 



DISEASES OF THE DIGESTIVE APPARATUS. 



other morbid sensations besides those of hunger and thirst are 

 evident ; they are produced by the want of certain salts. A simple 

 therapeutic instinct at the first start, this appetite soon degenerates ; 

 the diseased organism can only feel abnormal sensations, and the 

 licking-disease is a pathological craving in the clearest form it can 

 adopt. 



Frequency and distribution. The disease runs into a sporadic 

 or enzootic condition. In some years it affects a very large num- 

 ber of animals. It exists constantly in the Black Forest and in 

 many mountainous countries. 



In the Black Forest they call dry farms all those upon which 

 the disease is well established (Camerarius^). 



Nessler states that these farms are all located upon granitic soil ; 

 on those in regions having schistic soil the disease never prevails. 

 Nessler explains this geological influence by the disintegrating 

 property of the schistous rocks, which constantly furnish nutritive 

 salts, especially soda salts, to the soil, and consequently to plants. 

 The granitic soils, on the contrary, are composed of coarse grains, 

 which decompose very slowly. 



The disease exists endemically in certain localities, and may 

 persist for a long time, sometimes for a period of twenty years, 

 when the precaution of removing the animals to another locality 

 is not taken. The disease appears in other places only in very 

 dry years, when fodder is scarce. According to Haubner and 

 Spinola, there are farms where it makes the raising of calves 

 almost impossible. Cows which are imported contract it generally 

 in two or three years. 



As a general theory, pica is the appanage of poor countries and 

 small farming ; it appears mostly toward the end of the winter, 

 when food is wanting. Permanent stabling seems to favor its 

 development. 



Cows in an advanced condition of gestation, and good milkers, 

 are predisposed to it, while oxen are rarely attacked by it. 



The loss of saline matters from the cow's organism during 

 advanced gestation, or full lactation, is probably the cause of this 

 difference. Calves just weaned are frequently affected by it; 

 Lemke has observed the disease in sucklings. 



Symptoms. Lemke distinguishes two periods in the disease, 



1 Camerarius, Ephemerid. Nat. Cur., 1665-1721, describes them by the name of 

 'mllœ taheficiœ. 



