PHYSIOLOGY. 



belongs only to animals, whose perfec- 

 tion is in a direct ratio to the quantity of 

 this sensibility. There is some reason for 

 supposing that these two are not differ- 

 ent powers, but that they differ only in 



quantity. For inflammation, which is an 

 increased action of parts, raises organic 

 into animal sensibility in diseases of 

 bones, &c. 



Different stimuli, applied to the same 

 organ, determine the developement of 

 one or other of these powers : thus no 

 sensation is transmitted to the brain from 

 the passage of blood in the arteries, but 

 when an extraneous fluid is injected, the 

 animal's cries shew that he feels it. The 

 coats of the stomach experience in the 

 healthy state no perceptible impression 

 from the food, but very distinct and even 

 painful sensations are transmitted to the 

 brain when a few grains of poisonous mat- 

 ter are mingled with the aliment. The 

 animal sensibility excited on mucous mem- 

 branes by foreign bodies (as bougies in 

 the urethra, &c.) is quickly lost, and sub- 

 sides int* organic. 



Each Organ seems to have, indepen- 

 dently ofteccidental valuations, an original 

 quantity or dose of sensibility, to which it 

 returns after any deviation. In this con- 

 sists the peculiar life of each organ, and 

 from this arise the relations which it has 

 to extraneous substances. Hence excre- 

 tory ducts, opening on mucous mem- 

 branes, refuse admission to the sub- 

 stances passing along those canals. Hence 

 the lacteals absorb the chyle only. These 

 particular relations may also take place 

 with matters foreign to the body, as well 

 as with animal fluids, as we see in the 

 case of medicines acting on particular 

 organs, as cantharides, mercury, &c. 



Contraction is the common, but not the 

 universal mode of animal motions. For 

 the iris, corpus cavernosum, &c. dilate 

 when they move. Organic contractility 



is always and immediately connected with 

 organic sensibility, for there is no inter- 

 mediate function between these ; the or- 

 gan itself is the point in which the sen- 

 sation ends, and from which the principle 

 of contraction begins. The animal sensi- 

 bility and contractility are not so closely 

 united ; we may feel without moving : 

 here the nerves and brain perform their 

 functions between the action of the two 

 powers. 



Sensible organic, or, in other words, 

 involuntary and sensible contractility, cor- 

 responds very nearly to irritability ; while 

 the insensible seems more like tenacity. 

 To consider irritability as the exclusive 



endowment of muscles, is taking a very 

 contracted view of the subject. These 

 organs have indeed the largest portion, 

 but every part possessing life reacts, al- 

 though less manifestly, on the applica- 

 tion of certain stimuli. No rule is more 

 fallacious than that of estimating the mus- 

 cularity of a part by the action of arti- 

 ficial irritants. The organic and animal 

 contractilities cannot be converted into 

 each other as the corresponding sensibili- 

 ties can. 



The parts of the living body possess 

 also some powers which result merely 

 from their organization, and have been 

 denoted by physiologists under the epi- 

 thet of vis mortna. Thus they admit of 

 extension beyond the natural state from 

 extraneous impulse, and of contraction 

 when that impulse ceases to operate. 

 This extensibility and contractility are 

 independent of fife, and are terminated 

 only by death. The stretching of mus- 

 cles by moving a limb, the extension of 

 the skin over a tumour, its retraction 

 when divided, &c. are examples of these 

 powers. They have been confounded by 

 some physiologists with the insensible 

 organic contractility. 



A muscle exhibits all the powers now 

 enumerated. It contracts, in obedience 

 to the will, by its animal contractility ; 

 from the application of stimuli, by its or- 

 ganic sensible contractility. Its nutrition 

 and growth show the existence of orga- 

 nic insensible contractility ; and its re- 

 traction on a section exemplifies the con- 

 tractility of organization. The internal 

 organs of the body have only the three 

 last powers, and the white organs (car- 

 tilage, tendon, ligament, &,c.) only the 

 two last. While, therefore, the two first 

 properties exist only in certain parts, the 

 latter are found in all. Hence the orga- 

 nic insensible contractility may be select- 

 ed as the general character of all living 

 parts ; and the contractility of organiza- 

 tion as the common attribute of all living 

 or dead parts that are organically con- 

 structed. 



As for porosity, divisibility, elasticity, 

 and the other properties which living bo- 

 dies have in common with inanimate mat- 

 ter ; the> hardly deserve mention here, 

 because they are never exerted in their 

 whole extent, or in their genuine purity, 

 if we may use that phrase. Their results 

 are always affected by the influence of 

 the vital powers, which constantly mo- 

 dify those effects which seem to flow 

 most directly from physical, mechanical, 

 or chemical causes. 



