752 



NUTRITION. 



on the part of 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 it& 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 parts. 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 stoppage 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 



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 colliqualive 

 diarrhoea; for in both these, the increase and 

 depravation of the secretions are undoubtedly 

 to be regarded as the effects, and not the causes, 

 of the textural changes with which they are as- 

 sociated. Colliquative diarrhoea is a constant 

 occurrence on the last day or two of life in 

 animals reduced by starvation, and is accom- 

 panied by that foetid 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 unquestionably 

 the immediate cause of death. Partial atrophy 

 may occur in consequence of disuse of the organ 

 affected, occasioning inactivity in its formative 

 processes; or as a result of a deficiency of nu- 

 triment, occasioned by an obstruction to the 

 circulation. Of the operation of the former 

 cause we have many examples in the ordinary 

 processes of the economy. Thus the uterus is 

 atrophied, relatively to its previous condition, 

 as soon as parturition has taken place ; and the 

 mammary glands, when lactation has been dis- 

 continued. It is probably in part to this cause, 

 and in part to the diversion of the blood into 

 other channels, that we are to attribute the 

 atrophy of many parts, as the developetnent of 

 the system advances, which at an earlier period 

 were of large comparative size, such as the 

 corpora Wolffiana, the suprarenal capsules, and 

 the thymus gland. Many instances might be 

 adverted to, of the influence of suspension of 

 functional activity, as a result of disease or 

 injury, in producing local atrophy. One of the 

 most common cases is the atrophy of muscles 

 which is consequent upon their disuse. This 

 disuse will produce the same effect, whether it 

 be occasioned by paralysis, which prevents the 

 nervous centres from exciting the muscles to 

 contraction ; or by anchylosis, which inter- 

 poses a mechanical impediment to their use ; 

 or by fractures or other accidents, the re- 

 paration of which requires the limb to be kept 

 at rest. Or even if, without having suffered 

 from any injury, a limb be fixed during some 

 time in one posture, its muscles will be- 

 come atrophied, as is seen in the case of the 

 Indian fakirs. It has been shown by Dr. J. 

 Reid, that the atrophy of the muscles, and their 

 consequent loss of contractility, is not to be im- 

 puted to the withdrawal of nervous influence, 

 in any other way than as producing cessation of 

 their activity ; for he found that, when the mus- 

 cles of one leg of a frog, both whose crural nerves 

 had been divided, were daily exercised by gal- 

 vanism, they retained much more of their usual 

 size and firmness than those of the leg which was 



