Hereditary Diseases of Sheep and Pigs. 
39 
the symmetry and fattening capabilities of stock, it does so at 
the sacrifice of their general vigour and disease-resisting powers. 
Pigs are subject to most of tlie hereditary diseases of sheep, 
and in discussing this part of our subject we shall follow the same 
order as in Section II. 
Pigs are often attacked by epilepsy, which sometimes comes on 
very suddenly, distorting the countenance, especially the eyes, 
convulsing in the most violent manner all the muscles, obstruct- 
ing the respiration, accelerating the pulse, and leaving the ani- 
mal in a stupid, frightened state, from which it slowly recovers, 
often only to be again and again attacked in a similar manner at 
variable intervals of some hours, days, or weeks. The occurrence 
of an epileptic attack is sometimes preceded by restlessness and 
irritability, or by loss of appetite and dulness, and is often trace- 
able to some derangement of the digestive organs, and especially 
to constipation. The attacks often occur again and again without 
leaving any obvious change of structure in the brain or nervous 
system. In all such cases, however, some change of minute 
structure, though invisible to our present means of observation, 
must we believe exist; and there appears to be sufficient evidence 
of this in the fact of the disease being so specially apt to attack 
those animals that have once suffered from it. Now this altered 
condition of the brain is as much a part and quality of the indi- 
vidual as the shape of the snout or the appearance of the tail, 
and like these more external and palpable characters is capable 
of hereditary transmission. To mitigate an inherent tendency to 
epilepsy, the animals must be kept very clean, warm, and com- 
fortable, and supplied with a sufficiency of good digestible and 
somewhat laxative food. To eradicate it, the stock must receive 
an infusion of new blood, and this is especially necessary, as 
epilepsy in pigs depends in most cases on continued breeding in 
and in. 
A predisposition to lung diseases, and especially to bronchitis 
and pneumonia, sometimes appears hereditary among pigs, and 
is often indicated by a narrow chest, a general lanky and thrift- 
less appearance, and a great liability to suffer from coughs, 
readily excited by slight exposure to cold or wet, or even by 
changes of food. 
Among various of the larger and less improved varieties of 
pigs, many individuals may still be found with narrow carcases, 
flat ribs, a general coarse and washy appearance, and a want of 
balance and proportion among the more important organs of the 
body. Animals of such a formation are long in coming to ma- 
turity, consume large quantities of food, fatten slowly, and are 
moreover unusually liable to almost all disorders of the digestive 
organs, and especially to indigestion, with its usual symptoms of 
