20 
Hereditary Diseases of Sheep and Pigs. 
of many families both of sheep and pigs. But in some individuals 
of such families the tendency to the disease may remain altoge- 
ther latent ; while in otliers it may either naturally or from un- 
toward circumstances be so much more intense that a slight 
exposure to any of the ordinary exciting causes of consumption 
will determine at once the production of the disease. 
Rut it may be naturally inquired lioic are certain qualities of 
body and mind transmitted from one generation to another ? or, 
in other words, toliy do the progeny reseml)le their parents in 
form, temper, and liability to particular diseases ? 'J"o afford 
any satisfactory explanation of this we must look to the process 
of generation. The production of the embryo is determined hy 
the action of tlie male semen on the female ovum : but the semen 
is only a secretion of the male parent, endowed with its vitality, 
and probably impressed with its characters. The ovum pro- 
bably contains in miniature the constitutional peculiarities of 
the female parent ; and the embryo resulting from the congress 
ol these two is therefore a fusion, as it were, of certain vital parts 
derived from each parent, concentrating certain individualities of 
each, and endowed, we may suppose, with a part of the vital force 
of each. We may further believe that this vital force continues 
to regulate and conti-ol the nutrition and growth of the embryo 
throughout all stages of its development, and so renders it similar 
to the parentage from which that vital force was originally derived. 
But each parent impresses on the foetus not only its own 
habitual, material, and dynamic state, but also those more tem- 
porary and more accidental qualities which it may possess at the 
time of sexual congress. Children begotten by parents while in 
a state of drunkenness frequently become idiotic or insane. 
Burton, in his 'Anatomy of Melancholy,' says, " if a drunken 
man get a child, it will never likely have a good brain ;" and 
Diogenes is said to have remarked to a crack-brained, half-witted 
stripling, " Surely thy father begot thee when he was drunken." 
A child, begotten shortly after the father has had a severe injury 
of the head, has sometimes turned out of weak intellect ; and an 
ajit illustration of this is recorded by George Combe.* " A 
man's first child was of sound mind ; afterwards he had a fall 
from his horse, by Avhich his head was much injured : his next 
two children proved to be both idiots. After this he was tre- 
panned, and had other children, and they turned out to be of 
sound mind." The Arabs and other Asiatic nations appear well 
aware that those qualities which are most prominent in the 
parents at the time of sexual intercourse are reproduced in the 
offspring ; and, accordingly, in the breeding of horses, they give 
* Combe's Coustitution of Man. Fourth Edit. Pp. 44, 4.'). 
