VARYING ACTIVITY OF THE NUTRITIVE PROCESSES. 597 



site amount of cellular tissue be generated to hold the fatty matter ( 184). 

 But examples of Hypertrophy of particular tissues or organs are very com- 

 mon. Thus any particular set of Muscles, which is subjected to frequent and 

 energetic use, acquires a great increase in bulk ; as we see in the arms of a 

 Blacksmith or Waterman, the legs of an Opera-dancer, &c. The hypertrophy 

 of these muscles is a consequence of their increased functional activity ; which, 

 being produced by an exertion of the will, and unaccompanied with any in- 

 jurious effects on the system, can scarcely be regarded as morbid. But there 

 are many instances, in which the involuntary muscles acquire a greatly- 

 increased strength,, in consequence of an obstruction to their action, which 

 results from disease. Thus we see the right ventricle of the Heart become 

 hyperlrophied (and dilated at the same time), where chronic pulmonary dis- 

 ease produces a difficulty in the propulsion of the blood through the vessels 

 of the lungs; the muscular fibres of the Bladder become enormously hyper- 

 trophied, when stricture, diseased prostate, or other causes produce a demand 

 for increased expulsive force on the part of that organ ; 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. 



788. 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 con- 

 gestion of the Lungs, Liver, Spleen, &c., the bulk of these organs increases; 

 but chiefly by the production of an additional amount of interstitial Areolar 

 tissue, which may result (as we have seen) from the simple consolidation of 

 Fibrine ; and partly also (in the case of the spleen especially) 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 Bron- 

 chocele. So little is known of the normal office of this organ, that it cannot 

 be determined, whether its increased 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. 



789. 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 forma- 

 tive power in the tissues themselves, or from their too rapid disintegration. 

 The insufficiency of the supply of nutritive matter may depend either on de- 

 ficiency in the azotized substances ingested as food, or on imperfect perform- 

 ance of those processes by which they are converted into the plastic ele- 

 ment, Fibrine. 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 a want of vital power in the fibrine-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 



