Hereditary Diseases of Sheep and Pigs. 21 
the stallion and mare a smart jjallop before they bring them 
tog-ether. The endurance, strength, and spirit of both animals 
are thus more highly developed, and are believed to be trans- 
mitted to the offspring in this intensified state. The excitement 
of the gallop doubtless alters in some degree the conditions of 
the semen and ovum, and when the latter is fertilised the altered 
conditions still remain, and go on growing and strengthening 
throughout foetal life. The male offspring also have usually 
a special resemblance to the father, and the female to the 
mother ; and the resemblance is not confined to external form or 
mental attributes, but extends to defects and predispositions to 
disease. This is admirably illustrated by the propagation in the 
human subject of consumption and insanity which, in the 
majority of males, is inherited from the father, and in the majo- 
rity of females from the mother. The proportions are exhibited 
in the following Tables : * — 
Consumptive Males .. .. 
Consumptive Fathers . . | 
Consumptive Mothers . 
106 
63 or 
59 "4 per ct. 
I 43 or 
|46"6 per ct. 
Consumptive Females 
Consumptive Fathers 
Consumptive Mothers 
Insane ^Nlales .. 
Insane Fathers 
Insane Mothers 
117 
f 64 or 
(54 '6 per ct. 
( 53 or 
(45 "3 per ct. 
108 
f 47 or 
■ ■ ( 43 • 5 per ct. 
I 61 or 
■ ■ 1 56- 5 per ct. 
Insane Females 147 
Insane Fathers I j k .^^ * 
(45 '4 per ct. 
Insane Mothers ir ^.a 
1 54 "4 per ct. 
Among the lower animals the statistics of disease are as yet 
very meagre and imperfect, but we have sufficient evidence to 
prove that in them, as well as in the human subject, diseases are 
especially prone to descend from sire to son, and from dam to 
daughter. This may possibly be so far explained by the fact 
that the male offspring, as above remarked, usually resemble the 
sire, and the female the dam ; and whenever an animal especially 
resembles one of its parents in external and healthy characters, 
it is almost certain also to resemble it in those which are internal 
and morbid. See Addendum, page 42. 
In order to prevent or remove hereditary defects and diseases, 
great care must of course be exercised in the selection of both 
parents, so as to obtain them with as many good qualities as 
possible, with a strong and vigorous constitution, and freedom 
Irom those faults which are likely to interfere with usefulness and 
health. Care must especially be taken to avoid, for breeding 
purposes, all animals affected with any constitutional diseases, or 
blood- diseases, as they are sometimes called — such as scrofula, 
* Lugol on Scrofula, and Philips ou Insanity. 
