84 
Hereditary Diseases of Cattle. 
from which they grow ; are not contained in any distinct sac, 
and consequently rapidly extend themselves, and involve con- 
tiguous parts. Being merely the local symptoms of a generally 
depraved state of body, they are attended by great constitutional 
disturbance, and Avhen cut out generally reapjicar, either in the 
same or in some other part. Malignant tumours are composed of 
nearly the same constituents as non-malignant tumours, but contain 
these constituents in a very different condition, as well as in dif- 
ferent proportions. Both sorts consist of fat, gelatine, and 
albumen ; but this last is in excessive quantity in all malignant 
tumours, and the proportion in which it is present affords a 
tolerably fair criterion of the degree of the malignity of any par- 
ticular case. A tendency to the production of malignant tumours 
is hereditary. In cattle having this tendency a simple contusion 
is apt to give rise to a swelling, which, after passing through 
various intermediate stages, assumes the characters just described. 
At first it may be circumscribed and surrounded by a membrane 
preventing its extension ; tolerably soft, yielding, and moveable ; 
perfectly distinct from the surrounding parts ; not very painful — 
or, if pain be evinced, it is in the contiguous parts, and not 
in the swelling itself. It may continue in this condition for a 
considerable time, but the lymph of which it is composed is un- 
healthy, and does not become properly organised. From some 
local, or more often from some constitutional cause, the tumour 
becomes inflamed and painful, increases in size, softens, and after 
a variable time the skin ulcerates, and an unhealthy sanious dis- 
charge is poured out, irritating the skin over which it flows. 
Such are the characters of many tumours of a scrofulous kind 
which particularly affect the lymphatic glands, especially those 
about the throat, neck, and chest, and often impair deglutition 
and threaten suffocation. The salivary glands sometimes become 
involved. Similar tumours arc also occasionally found about the 
udder and external organs of generation. Tliey often affect young 
and rapidly-growing cattle when pastured in cold and elevated 
districts. They may sometimes be removed, and the parts healed 
up by the use of external stimulants, aided by equable pressure ; 
but the more effectual practice is to dissect them out with the 
knife, or, after making a free incision, to cauterize their internal 
surface ; in all cases giving, during convalescence, tonics and sti- 
mulants, with a nutritious diet and comfortable housing. 
But there is another variety of tumour, resembling the scro- 
fulous tumour, and often mistaken for it. This is the cancerous 
tumour. It is malignant, and indeed almost impossible of cure ; 
occurs only among animals of a depraved constitution, .and is 
decidedly hereditary. It assumes various forms, of which the 
schirrous is the most common among cattle. Schirrous tumours 
