Hereditary Diseases of Cattle. 
83 
tlie corrcsponcling disease in man is usually held to be so. Its 
special exciting causes are the same as those of consumption, 
and include bad food, insufficient shelter, and all other debili- 
tating influences. Like consumption, it is also frequently de- 
veloped by breeding in-and-in — a system which, unless very 
carefully and judiciously practised, causes a speedy deterioration 
of the stock, rendering them delicate and difficult to rear, often 
inducing abortion in the female, and defective vigour and effem- 
inacy in the male — the invariable consequences of the infringe- 
ment of that natural law which forbids sexual connection between 
animals too nearly related to each other. 
3Jalir/iiant tumours affect cattle more frequently than any of 
the other domesticated animals. They are common amongst 
stock in badly-sheltered localities, and especially along those 
parts of the island exposed to east winds, with their accompany- 
ing damp and cold. But although such tumours were probably 
caused in the first instance by external circumstances, and are 
capal)le of being so induced in perfectly healthy stock, still 
animals affected by them transmit to their offspring a strong 
tendency to their development — a striking illustration of the 
hereditary nature even of acquired peculiarities and diseases. 
We know at present of several stocks which have been affected for 
many generations by warts or angle-berries, in which it would be 
difficult to discover an animal entirely free from such excres- 
cences, or which had never been affected by them. We have 
also met with other stocks in which tumours of a more serious 
character are almost equally prevalent. It is a matter of popular 
belief that those tumours known as chjers are hereditary ; and 
we have found them particularly prevalent, and often fatal, in 
many stocks which have come under our own observation. For 
example, a friend very recently purchased a cow to all appear- 
ance quite healthy, but which soon became affected with clyers ; 
and, upon inquiring into the animal's pedigree, he discovered 
that many of the stock from which it came had been seriously 
affected by the same disease, and that it had prevailed amongst 
them for several generations. 
Tumours are divisible into two great classes, malignant and 
non-malignant. The latter are mere excrescences, analogous to 
the tissues of the body, and so far normal textures ; they do 
not vitiate or destroy the tissues in which they appear ; are 
often contained in a cyst or sac, and when removed by exci- 
sion they are not usually reproduced ; and, being merely local 
in their effects, they rarely cause constitutional disturbance : they 
are also very rarely hereditary. Malignant tumours, on the other 
hand, consist of materials in an abnormal condition ; they, sooner 
or later, run on to softening, and cause breaking up of the tissues 
G 2 
