352 OF NUTRITION. 



activity is more under the control of the individual, and is therefore less 

 constant. Thus, in Man, we continually notice that the duration of the 

 powers of the Brain and the Generative system is the longest, when 

 these organs have been moderately exercised ; and that it is much cur- 

 tailed by the excessive use of either. The duration of their activity, 

 however, is not increased by partial or entire disuse of the organs ; for 

 this induces a state of atrophy, on the principles already mentioned. 

 Now we have every reason to believe, that what is true of individual 

 parts and organs, is true also of the whole structure ; and that the 

 existence of the entire bodily fabric may thus come to an end, without 

 any special disease, in consequence of the limit originally set to its 

 powers of self-renovation. It is but rarely, however, that this occurs ; 

 the various accidents of life, the neglect of ordinary precautions for the 

 preservation of health, and hereditary tendencies to various kinds of 

 morbid action, being too frequently the means of cutting off the term of 

 Human existence, long before its natural expiration. 



4. Disordered Conditions of the Nutritive Processes. 



631. Having thus passed in review the general conditions, under 

 which the ordinary Nutritive processes take place, it may be well to 

 add a few words in relation to two of their abnormal states ; one or 

 other of which is concerned in a very large proportion of the diseases 

 that afflict the human race. In one of these, there is a tendency to the 

 excessive production of fibrine in the blood ; whilst in the other, there 

 is a want of the proper nutritive power in the tissues, which is appa- 

 rently due to an imperfect elaboration of that important material. The 

 one of these conditions is termed Inflammation ; whilst the other, which 

 is less active, but more insidious, is known as the Tubercular Diathesis. 



632. The extraordinary tendency to the production of Fibrine in the 

 blood, which has been already noticed ( 531) as one of the most im- 

 portant characters of Inflammation, seems to be always conjoined with 

 a depressed vitality of the tissues of some part of the body, which indis- 

 poses them to the performance of their regular nutritive operations ; and 

 this part may undergo a variety of changes, according to the degree in 

 which it is affected. The depressed condition of its nutritive operations 

 involves, on the principles explained in the preceding chapter, a languor 

 in the movement of blood through it, together with a distensible state 

 of the capillaries, which causes them to contain a far greater amount of 

 that fluid than under ordinary circumstances. On the other hand, there 

 is a tendency to the production of an increased amount of plastic mate- 

 rial in the blood, as if for the reparation of the part whose vitality is 

 lowered. What is the immediate cause of this production is still doubt- 

 ful ; but we see the consequences of the deficiency of it in those asthenic 

 or unhealthy Inflammations, which so frequently involve the destruction 

 of a large amount of tissue ; the degeneration of the part first affected 

 soon extending itself to others, if there be no limit set up by the repara- 

 tive powers of the blood. In ordinary or sthenic Inflammation, of which 

 the increase of fibrine in the blood, and a diminution in the power of 

 appropriating it on the part of the tissues, are the most characteristic 



