PHYSIOLOGY. 



551 



As man stands highest in the scale of beings 

 which we have an opportunity to observe, he is the 

 most interesting subject of physiology, both because 

 animal life is most developed in him, and because 

 his animal life is intimately connected with his in- 

 tellectual and moral life ; for, whatever may be the 

 belief respecting the state of the soul before or 

 after our existence on this earth, it is certain that 

 during the time of our earthly life, the soul and 

 body are, in more than one respect, intimately uni- 

 ted. Under this view several German philosophers 

 have treated physiology, and attempted to draw 

 from it illustrations for the higher anthropology. 

 Without going into that subject at present, we shall 

 give here a brief outline of the German mode of 

 treating physiology, which is probably less familiar 

 to our readers than that of France and Britain. 

 The human frame consists of a multiplicity of or- 

 gans, which are constantly in a state of mutual ex- 

 citement and mutual restraint. The chain of causes 

 and effects is endless, yet observation has discovered 

 certain series and orders, called systems. Thus we 

 have the systems of reproduction, irritability and 

 sensibility, (q. v.) The province of the reproductive 

 system is to preserve and unfold the organization. 

 Matter is in uninterrupted change : it undergoes a 

 constant union and separation. This is as true of 

 the animal frame as of the lower forms of matter. 

 There is a constant succession of states, and the 

 whole life of the organization consists, as it were, of 

 innumerable smaller circles of life, beginning with 

 that of the simple substances, each of which runs 

 through certain changes, and then begins anew, and 

 proceeding thence to the higher organs and systems. 

 This constant change in the animal frame requires 

 a constant introduction of new matter into the sys- 

 tem, and a constant separation of that matter which 

 has completed its brief tour of duty, and must be 

 thrown off as useless. The new matter received 

 has to undergo a series of changes to adapt it to the 

 purposes of animal life. These changes are effected 

 by means of a number of organs, whose form, con- 

 struction and activity correspond to their destina- 

 tion. These are the organs of ingestion and diges- 

 tion, the mouth, throat, stomach and intestines, the 

 absorbing vessels of the intestines, which in their 

 course form glands, then canals, ending at last in 

 one canal. (See Chyle, Digestion, and Dyspepsia.) 

 The received matter becomes purer and purer, that 

 is, fitter for animal life, and eventually becomes 

 blood (q. v.), which change is effected in the lungs 

 (q. v. ), from which the blood collects in the left 

 cavities of the heart. (See Heart for an account of 

 the circulation of the blood.) The blood is a fluid 

 endowed with life, and is spread all over the organi- 

 aation, diffusing new matter and life in innumerable 

 currents. The arterial system penetrates every or- 

 gan, and every organ gives to the matter thus re- 

 ceived its peculiar character. Part of this blood, in 

 the shape of coagulated fibres, assumes the first or- 

 ganic form, the cellular texture (an animal crystalli- 

 zation, as it were), attaches itself to the already ex- 

 isting matter of the same kind, in order to assist the 

 latter, if it is yet in the process of formation, or to 

 supply the place of that whose virtue is exhausted, 

 and, by further processes, gives rise to the various 

 other parts of the human body, as the cellular tex- 

 ture, the various membranes, glands, hairs, bones, car- 

 tilage, muscles, arteries, the capillary system, nerves, 

 brain, &c. These single parts, by various combina- 

 tions, form thecom pound organs, whose functions vary 

 with their composition. Another part of the blood 

 is destined to be changed into various fluids ; this is 

 effected by the function of secretion, for which se- 

 veral organs are destined. To these belong the se- 



cretion of the saliva in the salivary glands, of the 

 gastric juice in the stomach, of the gall in the liver, 

 milk in the breasts, of the mucus in the mucous 

 membranes, &c. After the various forms of or- 

 ganic matter have run through their short circle of 

 life, they lose their character of animal life and ac- 

 tivity, change their peculiar form, are dissolved, ab- 

 sorbed in proper canals, and thrown out. This is 

 done by the absorbing lymphatic vessels, by the kid- 

 neys and urinary passage, the skin, &c. 



The system of irritability (q. v.) is composed of 

 the fibre formed out of the blood, and endowed with 

 a higher life, and consists of the muscular fibre, 

 which possesses the faculty of shortening itself by 

 contraction. Aggregations of these fibres form a 

 muscle. Some of these are hollow muscles, for the 

 reception and transmission of fluids, as the heart 

 and the muscular membranes. The others are con- 

 nected with the system of bones, and serve for 

 voluntary motion. (See Muscles.) The system of 

 sensibility consists of the matter in the highest stage 

 of life, and forms the whole system of the nerves. 

 (See Nerves, and Brain.) These systems are closely 

 connected, and are combined in each organ : thus 

 we find every where cellular texture, membrane, 

 vessels, &c., and nerves which diffuse a higher life 

 throughout the organs, and produce, by their gener- 

 al connexion, a harmony in the functions of all the 

 organs, which, if undisturbed, is called health. To 

 the series which gives rise to this harmony of the 

 functions belong also the activities of the soul, in 

 so far as the material organization influences them, 

 or the soul influences the material organization. 

 For, though the life of the soul is superior to the life 

 of the body, the latter only following unchangeable 

 laws of nature, the former being guided by reason 

 and volition, yet the close union of both, and their 

 mutual operation, cannot be denied. The material 

 organization affects the soul by the cerebral system 

 and nerves, the soul receiving ideas of outward 

 things through the senses (see Nerves) ; and though 

 the cerebral system belongs peculiarly to the soul, 

 yet it is nourished and maintained by the same 

 means as the whole animal organization ; and this cir- 

 cumstance, and perhaps the connexion of the nerves of 

 the systems of sensibility and reproduction, give rise 

 to what we call instincts and impulses connected 

 with the physical wants. Further, there seems to 

 exist a constant yet silent influence of the material 

 organization on the higher nervous system and the 

 brain, owing to the support of these organs by the 

 blood, and to the connexion in which all organs 

 are kept through the nerves ; and these circumstances 

 appear to explain the causes of the various tempera- 

 ments and the change in our dispositions. The soul, 

 on the other hand, operates upon the bodily organi- 

 zation by many voluntary acts, which affect the or- 

 ganic life, by the restraint of the appetites, and by 

 the activity which its own operations necessarily 

 excite in its organ, the brain ; and, finally, by the 

 direct influence of certain passions and emotions, on 

 particular parts of the frame. All these points are 

 minutely treated in physiology. 



The history of physiology is intimately connected 

 with that of medicine. It began with scanty mate- 

 rials and hypotheses. Hippocrates had but a very 

 imperfect knowledge of the human organization, and 

 very limited views of the origin of life. Galen, pos- 

 sessing a better knowledge of anatomy, composed a 

 better system of physiology. From him originated 

 the division of the functions into vital, animal and 

 natural functions, which has maintained itself down 

 to our time. After the middle ages had gone by, 

 the more thorough study of anatomy led to a better 

 system of physiology. Harvey's discovery of the 



