160 



IMIY-sHMJlIAI'HY 



PHYSIOLOOY 



research ; Mantegaua, in /Vi.y.v/<.</<iy !<! Kf/int- 

 tiiin i ('onteinp. Si-. Series, 1890), claims U) have 

 liegiiii win-re Darwin left off. I'iil.-iit, in Muni/; 

 Mini rhi/si<i'iH<iiii,k ('Jd el. 1886), proceeils on the 

 nl, \ ions furt that tlie most valuable ilata are not to 

 ! derived from the bony framework of the coun- 

 tenance, lint in the mobile parts which express 

 emotion; features which constantly express the 

 satin- I'motioii come to be stamped with permanent 

 physiognomic characters. Pathological physiog- 

 nonn is a systematized effort todiafBOM mental or 

 liodily ailments by examination of the varying 

 facial expression. Another practical application 

 of physiognomic >tiiily is fonml in what has been 

 called CriinimiltM/y ; sec Havelock EMU, The 

 Criminal i < 'oiiteinp. Sc. Series, 1891). 



Physiography, a term formerly used of a 

 branch of mineralogy, was adopted oy Professor 

 llaxlev as a convenient name for an exposition 

 of the principles that underlie physical geography, 

 ami including the elements of physical science. 

 Phy-iogiaphy is thus understood to involve a com- 

 pi-ii'li'iu- discussion of gravitation, heat, the com- 

 |Misition of the crust of the earth, the movements 

 of the .sea, the phenomena of the atmosphere, and 

 many connate subjects, treated in this work under 

 separate, heads. See (iKOKKAl'HY. 



Physiologus. See BESTIARY. 



I'll >siol Oil V (<Jr. iifii/xi* and logos, 'discourse 

 ii]>on nature ) is the science which treats of the 

 behaviour of living beings, and of the functions of 

 their parts. It is thus the sister-science to Mor- 

 phology (f|.v.), in which the outer form of living 

 creatures and the structure and arrangement of 

 their part* are considered. Both are included 

 iiiider the more general term Biology (q.v.). A 

 peculiar use of the term /ihi/nii is due to Himxi 

 crates, who applied it to a spiritual entity winch 

 he sup|K>sed to l>e everywhere prawn t, and to keep 

 the processes of the liody ill order. This use of 

 tin- word is still kept alive in oft-repeat**! phrases, 

 ax when in speaking of a sick |>ersoii it is recom- 

 mended that the cure l>e left to nature. There is 

 an Animal Physiology, of which this article will 

 mainly treat, and a Vegetable Physiology iq.v. i; 

 also n Comparative Physiology, which, however, is 

 still very imperfect, for the details of the life-pro 

 caMCii have been investigated in not more than a 

 dozen animals. Indeed, comparative physiology 

 consists diielly of a series of inferences :t s to 

 function from comparative morphology, and these 

 must lie often erroneous. There is a still wider 

 science, which might Im called Universal Physi 

 ology. For as all the organs of the body are 

 mutually related, so that if one be deranged nil 

 the others will lie more or less affected, so are 

 then- close relationships lielwecn the various 

 en' ilures of the glolie. Thus, to quote SI-IUJMT, 

 .tumult I. if'- I 1HSI ) : 'If the American prairies 

 were to cease to produce gras. the first result 

 would lie the utter extinction of the now numerous 

 herds of buffaloes, and on theii existence depends 

 that of the surviving remnant of the ancient Indian 

 imputation of America. If the various insectivorous 

 birds of North America were exterminated, within 

 a very few years beyond a doubt all the produce of 

 the lidi agricultural districts of that continent 

 would IK- destroyed. If we change the mode of 

 life of any single animal, the change will instantly 



hare HII intlneiii n all tlic oilier animals whose 



healthy existence was in any way de|x>iidcnt on 

 it" normal function before it was' altered . ' The 

 most obvious relation of this sort is (hat which 

 exi-ts bciwi-cn plant* and animals; similar ones 

 hold good for human lu-ings in their relationship 

 to other liiiiig things, and to each other. Thus 

 we see in Political Economy, the science which 



treats of the laws of human activities, a depart- 

 ment of the science of physiology. A still wider 

 significance might lie given to the science ; for 

 in view of the fact that the intimate relations 

 iHjtween chemical, physical, and living processes 

 are becoming daily more evident, it would ! quite 

 consistent that morphology should deal not only 

 with the forms of plants and animals, hut also 

 with those which the dust assumes in the ciistal. 

 pyramid, and star, while physiology would 'treat 

 of the forces and chemical processes concerned. 



Knowledge of the Imdily functions has been 

 gained in three ways : ( 1 ) by olwerving the normal 

 states of living tilings; (2) by experiments upon 

 these: (3) by studying the processes of disease. 

 No science can advance rapidly or with certainty 

 without experiment, and most of our precise know 

 ledge of physiology has lieen gained in this way. 

 from the time when ( ialen proved that the art' 

 during life contain Mood, or when Harvey demon 

 M rated the circulation of that blood. As an 

 example of how we may learn from disease, we 

 may note the discovery that the spleen produces 

 white blood-corpuscles, following from the obser- 

 vation that in morbid enlargement of that organ 

 the blood contains an increased number of these 

 cells. 



The functions of the Ixxlv consist of ( I ) Move 

 ment, (2) Nutrition, (3) the activities associated 

 with the Nervous System, (4) Crowth and Repro- 

 duction the latter lieing considered as continued 

 growth. Movement is performed by the contrac- 

 tion of muscles, definitely arranged, especially 

 with relation to the skeleton or supporting strnc 

 ture. Nutrition is a general term including all 

 those processes concerned in the supply of matter 

 and energy to the body, and the removal of waste 

 matter, ft may be considered under three head- 

 ings : (1) the introduction of food into the body 

 ami its carriage to the tissues; (2) the changes of 

 this matter within the tissues; (3) the removal of 

 waste matters from the tissues and from the liody 

 Excretion (q.v.). The first include:-. () the eating 

 and drinking of solid and liquid food, and the 

 intaking of oxygen, a part of Respiration (q.v.): 

 (li) the Digestion (cj.v.) of the food ; (<) its absorp 

 tion into the Blood (q.v.); (tl) the circulation of 

 the blood and its associate tin 1 Lymph iq.v. i. by 

 means of which the tissues are bathed in a stream 

 of food, and the waste matters removed fiom 

 them. The nervous system is the co ordinatoi of 

 all the processes of the liody ; it consists of the 



Brain, Spinal cord. Sympathetic syst , and the 



associated Nerves and smaller Canglia; in close 

 connection with it are the sense organs, the exes, 

 ears, nose, tongue, and general nerves of touch and 

 temperature: the brain is the seal, or at all events 

 (he chief seal, of consciousness, and the 'organ ' of 

 thought and other mental processes. The fnnc- 

 lions of the !MM|\- are dealt with in sepaiate 

 articles ; here we shall give a short account of 

 their lelations to each other. 



Let us first consider the life of the simplest 

 animals. Almost invisible to unaided sight, flourish 

 ing in the stagnant water of ]>nds. without separ- 

 ate organs, they are little more than tiny masses 

 of jelly like' Protoplasm (q.v.). Their life seems 

 to consist in movement, nutrition, growth, and 

 reprodilclion : possibly they possess the elements of 

 consciousness. For movement a source of energy 

 is required ; this is found in their food minute 

 organisms, and organic particles dissolved in the 

 water in which they live. These consist of sub 

 stances of high pOtHtU energy. They arc' either 

 plants which are able to utilise the energy of the 

 sun for their growth, or remains of plants or 

 animals which nave fed upon plants (see VKLI- 

 TABLE PHYSIOLOGY). Thus we see in animal 



