826 



HYPERTROPHY AND ATROPHY. 



likewise. The blood in these cases is chiefly 

 contained in capillaries and veins, the ramifica- 

 tions of which will be found fully injected. 

 The dependent parts of all the vascular tissues 

 and organs of a body thus placed, exhibit 

 similar appearances. The scalp on the occiput, 

 the posterior lobes of the brain, and the 

 cerebellum are much more injected than the 

 anterior parts of the same textures. The pos- 

 terior parts of the lungs, of the stomach and 

 intestines, of the spleen, liver, and kidneys 

 exhibit the same state of vascular congestion. 

 That this results altogether from position and 

 the blood in the vessels obeying the universal 

 law of gravitation, may be clearly proved by 

 reversing the position of the body, when after 

 a little time the blood will desert the former 

 dependent but now elevated parts, and those 

 portions of the texture which before were almost 

 devoid of blood from their elevated position, 

 now have their vessels filled with it. 



When hyperaemia results from a mechanical 

 obstacle to the circulation, it is not accumulated 

 at one part of an organ or viscus, but all parts 

 appear equally gorged with the blood. In 

 certain diseased states of the heart and liver, 

 the intestinal canal presents an example of this 

 general hyperaemia, owing to the mechanical 

 obstacle to the free circulation of the blood in 

 the right heart. The circumference of the 

 intestine is every where reddened by the blood 

 accumulated in its capillaries. 



Audral, by whom of late years the term hy- 

 peraemia itself was brought into use in morbid 

 anatomy, gives the following varieties of it. 

 1. Active or sthenic hyperaemia, denoting the 

 state indicated by the ordinary expression 

 acute inflammation. 2. Passive or asthenic, 

 resulting from diminished tone in the capil- 

 jary vessels. 3. Mechanical, from an obstacle 

 to the venous circulation. 4. Cadaveric or 

 post-mortem, being the result of those physical 

 and chemical laws to which all inorganic 

 matter is subject, and to which all organized 

 bodies are also subjected when the vital spark 

 has ceased to animate them.* This last variety, 

 moreover, he subdivides into two genera. 

 First genus, hyperaemia produced at the mo- 

 ment of death. Cause; the contractility of 

 tissue which resides in the small arteries, con- 

 tinuing to act after the heart has ceased to beat. 

 Second genus, hypersemia produced at a certain 

 period after death. This genus comprehends 

 the following species: 1. Hyperaemia by hy- 

 postasis or dependent position. 2. Hyperaemia 

 by transudatton of the blood or of some of its 

 component parts through the parietes of its 

 vessels. 3. Hyperaemia by chemical affinities. 



Anamia, a term long in use to express a 

 general exsangueous and cachectic condition 

 of the body, is also applied to a local state 

 of exsangueousness. Any cause which would 

 impede or cut off the wonted supply of blood 

 to a part will occasion this condition in it ; the 

 diminution in the calibre of the principal artery 

 of an organ, from mechanical pressure or disease 



* Path. Anat. by Townscnd, vol. i. p. 15. 



in the vessel, or a depressed state of the nervous 

 influence. Hyperaemia of one organ may give 

 rise to anaemia of another, the former as it 

 were attracting the blood away from the 

 latter. 



The general condition of anaemia is not un- 

 frequently brought under the physician's notice 

 either as the result of some excessive and long- 

 continued hemorrhage or of some deranged 

 state of general nutrition, giving rise to a deterio- 

 ration in the quality of the blood, or a general 

 deficiency in the powers of the nervous in- 

 fluence. The surface of the body is pale, the 

 mucous membranes, as far as they can be seen, 

 partake of the same exsangueous state, the 

 secretions are defective and vitiated, the tone 

 of the muscular and vascular systems is con- 

 siderably diminished, and this state may go on 

 without any specific morbid change in any 

 organ, beyond its participation in the general 

 scanty supply of the blood, or it may co-exist 

 with an organic disease, which, although it 

 may have been at first the result of the primary 

 exciting cause of the anaemia, now serves to 

 increase it, or offers the greatest impediment to 

 its removal. 



(R. B. Todd.) 



HYPERTROPHY AND ATROPHY, 



super ,a,priv., and Tge<pu,nutrio},(in morbid ana- 

 tomy). When any organ or tissue has acquired 

 a certain increase of developement, without 

 any manifest alteration of its natural structure, 

 it is said to be in the state of hypertrophy 

 the increase being due to a greater activity 

 of the nutritive process in the part affected. 

 A familiar example of hypertrophy, although 

 not morbid, is afforded by the augmentation 

 which muscular fibre acquires in consequence 

 of increased action. If the biceps muscle of 

 one arm be actively exercised, while that of the 

 other does not undergo any considerable degree 

 of action, the former acquires a great increase 

 of size, it becomes denser and firmer, and 

 manifests the physical and vital phenomena of 

 the muscular tissue with more than ordinary 

 energy. 



There is no texture in the body which does 

 not occasionally exhibit evidence of the hyper- 

 trophous condition. The circumstances which 

 favour its production are an abundant and a 

 free afflux of blood to the part, an energetic 

 nervous influence and an increased demand 

 upon the organ, or increased exercise if it be 

 muscular; and indeed these are the almost in- 

 variable conditions under which hypertrophy is 

 manifested. The heart becomes hypertrophous 

 under an exalted nervous influence, or from a 

 necessarily increased exercise from the effort to 

 overcome some obstacle to the free circulation of 

 the blood through its cavities ; one kidney 

 acquires a great increase of size if the other 

 one be incapable of performing its function. 

 It may be said that the liver is in a state of 

 hypertrophy in the foetus in utero, for it has 

 a larger supply of blood than in extra-uterine 

 life, and the lungs have not as yet begun to 

 share with it in the office of decarbonizing the 



