752 
on the pepot the bladder; and those of the 
stomach also become so in cases of stricture of 
the pylorus. As an instance of hypertrophy of 
a secreting organ in consequence of an undue 
excitement of its function, we may notice the 
enlargement which usually takes place in the 
kidney, when its fellow is incapacitated by 
disease, And the nervous system presents us 
with a very remarkable case of hypertrophy of 
a part resulting from over-excitement of its 
function ; for if young persons who naturally 
show precocity of intellect are encouraged 
rather than checked in the use of their brain, 
the increased nutrition of the organ (which 
grows faster than its bony case) occasions 
pressure upon its vessels, it becomes indurated 
and inactive, and fatuity and coma are the 
result. Local hypertrophy may be induced 
also by local congestions ; but in such cases it 
will usually be found that the form of tissue 
produced is of the lowest kind, unless the 
functional activity of the part be increased by 
the. congestion. Thus when disease of the 
heart produces long-continued congestion of 
the lungs, liver, spleen, &c., the bulk of these 
organs increases; but chiefly by the produc- 
tion of an additional amount of interstitial 
areolar tissue, which may result (as we have 
seen) from the simple consolidation of fibrin ; 
and partly also (in the case of the spleen espe- 
cially) by the gorging of their distensible veins 
with blood.—One of the least explicable cases 
of hypertrophy is that which takes place in the 
thyroid gland, causing bronchocele. So little 
is known of the normal office of this organ, 
that it cannot be determined whether its in- 
creased size be due to an increased activity of 
its functional operations, or to an unusual 
formative activity in its tissue, depending on 
some hidden cause. The connection of this 
disorder with causes which affect the whole 
constitution, rather than individual parts, would 
seem to indicate the former. 
When the waste of the tissues is more rapid 
than their replacement by nutrition, atrophy is 
said to take place; and this may affect either 
the whole body, or individual General 
atrophy, marasmus, or emaciation, may result 
from an insufficient supply of plastic matter, 
from want of formative power in the tissues 
themselves, or from their too rapid disintegra- 
tion. The insufficiency of the supply of nutri- 
tive matter may depend either on deficiency in 
the azotized substances ingested as food, or on 
imperfect performance of those processes by 
which they are converted into the plastic 
element,—fibrin. Hence, even when there is 
an ample supply of food, atrophy- may take 
place to a very severe extent, in consequence of 
disordered digestion, or of want of vital power 
in the fibrin-elaborating cells. Again, we have 
reason to believe that the formative power in 
the tissues themselves may be diminished, so 
as to check the process of nutrition, even when 
the plastic material is supplied ; thus there 
seems to be a complete stop of this action 
in fever, and a diminution of it in that irritable 
state of the system, which results from excessive 
and prolonged bodily exertion or anxiety of 
NUTRITION. 
mind, especially when accompanied by want of 
sleep. It is difficult to separate this cause, 
however, from mal-assimilation on the one 
hand, or too rapid decay of the tissues on 
the other: for we know that, in such states, 
there is a tendency to imperfect elaboration of 
the fibrinous element, and at the same time 
an unusually rapid disintegration, as mani- 
fested by the increased amount of urea in the 
urine. The influence of excessive waste in 
causing atrophy of the body is well shown in — 
the cases of diabetes mellitus and colliquative — 
diarrheea ; for in both these, the increase and — 
depravation of the secretions are a 
to be regarded as the effects, and not the causes, — 
of the textural changes with which they are as- 
sociated. Colliquative diarrhea is a constant — 
occurrence on the last day or two of life in 
animals reduced by starvation, and is accom- 
panied by that feetid odour of the body, which 
indicates that decomposition is already going on 
throughout the system. The same thing occurs: 
as the ordinary termination to many diseases of 
exhaustion ; in which inanition is unquesti y 
the immediate cause of death. Partial 
may occur in consequence of disuse of the organ 
affected, occasioning inactivity in its formative 
processes ; or as a result of a deficiency of nt 
triment, occasioned by an obstruction to— 
circulation. Of the operation of the formel 
cause we have many examples in the ordinar 
processes of the economy. Thus the uterus 
atrophied, relatively to its previous condition 
as soon as parturition has taken place; and: 
mammary glands, when lactation has been dit 
continued. It is probably in part to this cau: 
and in part to the diversion of the blood in 
other channels, that we are to attribute | 
atrophy of many parts, as the developement 
the system advances, which at an earlier y 
were of large comparative size,—such as 
corpora Wolffiana, the suprarenal cap 
the thymus gland. Many instances mig 
adverted to, of the influence of suspension 
functional activity, as a result of disease 
injury, in producing local atrophy. One of 
most common cases is the atrophy of mus 
which is consequent upon their disuse. — 
disuse will produce the same effect, whet 
be occasioned by paralysis, which preven 
nervous centres from exciting the m 
contraction ; or by anchylosis, which 
poses a mechanical impediment to 
or by fractures or other accidents, 
paration of which requires the limb tot 
at rest. Or even if, without having s 
from any injury, a limb be fixed during 
time in one posture, its muscles wil 
come atrophied, as is seen in the case” 
Indian fakirs. It has been shown by 
Reid, that the atrophy of the muscles, am 
consequent loss of contractility, is not te 
puted to the withdrawal of nervous in 
in any other way than as producing ce: 
their activity ; for he found that, when th 
cles of one leg ofa frog, both whose crural | 
had been divided, were daily exercised b 
vanism, they retained much more of theit 
size and firmness than those of the leg whic 
rs 
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