VARYING ACTIVITY OF THE NUTRITIVE PROCESSES. 459 



cessive 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 from too rapid decay of the tissues 

 on the other : for we know that, in such states, there is a tendency to imper- 

 fect elaboration of the Fibrinous element, and at the same time an unusually 

 rapid disintegration as manifested 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 Diarrhoea ; 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 associated. 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. 



605. 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 nutriment, 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 discontinued. 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 development of the system ad- 

 vances, 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 func- 

 tional 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 interposes a mechanical im- 

 pediment to their use ; or by fractures or other accidents, the reparation 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 become atrophied, as is seen in the case of the Indian Fakirs. (See 382). 

 Similar facts may be adduced, in regard to Atrophy of Nerves, from interrup- 

 tion of their normal function. Thus when the Cornea has been rendered so 

 opaque by accident or disease, that no light can penetrate to the interior of the 

 eye, the Retina and the Optic nerve lose, after a time, their characteristic 

 structure ; so that scarcely a trace of the peculiar globules of the former, or of 

 the nerve-tubes of the latter, can be found in them. These and similar facts 

 are readily understood, when connected by the general principle formerly laid 

 down, that every proper vital operation involves an act of nutrition ; in such 

 a manner that, whilst the vital properties of any part are dependent upon its 

 due nutrition, the amount of its nutrition will in return depend upon the 

 degree in which these properties are exercised. Partial Atrophy may depend, 

 however, upon causes of a purely mechanical nature ; such, for example, as 

 produce an interruption of the current of Blood through the part. This may 

 result from changes in the Arteries supplying it ; such as ossification, or other 

 forms of obstruction. Or it may be consequent upon disease in the part itself; 

 as when the deposits produced by Inflammation tend to contract, and thus to 

 press upon the vascular structure, which frequently happens in the lungs, 

 liver, and kidneys ; or when the inflammation occurs in the vessels themselves, 



