Februart 25, 1887.] 



scmwcu. 



195 



blood to the brain be clamped, thus cutting off 

 the oxygen-supply and abolishing the removal 

 of waste, or should the blood passing through 

 them be artificially warmed, thus hastening the 

 chemical changes in the nerve-centres w^ithout a 

 corresponding increase in the rapidity of food- 

 supply and waste-removal, the deep and energetic 

 breathing of dyspnoea soon shows the pressing 

 need of the centre for fresh oxygen ; and the ani- 

 mal may die, as far as its brain is concerned, in 

 the convulsions of asphyxia, though the great 

 bulk of its body is unaffected, and lives on in perfect 

 rest so soon as the exhausted brain can no longer 

 stir its muscles to contraction. 



If we arrange a narcotized living animal in such 

 a way as to observe the changes in the amount of 

 its arterial blood -pressure while supplying air by 

 artificial respiration, it will be observed that the 

 pressure rises when the respiration fails ever so 

 little, and the elevation is most marked when the 

 muscular contractions of extreme dyspnoea ap- 

 pear. Now, it is this arterial pressure which 

 drives the nutrient blood on its way. The blood- 

 current is stronger and swifter, the greater the 

 pressure ; and the result of such a change is to pre- 

 sent each tissue with a more abundant supply of 

 oxygen and other food-materials. The rise of 

 pressure noticed in the first instance was due to 

 the contraction of the living walls of the blood- 

 vessels throughout the body : they responded di- 

 rectly, or were made to respond indirectly through 

 their motor nerves, to the need of the oxygen in 

 their local areas and in the brain ; and the result 

 of this action was to supply with all despatch the 

 respiratory centre with whatever store of oxygen 

 there was in the blood. So we have the all-im- 

 portant fact of the mutual helpfulness of the 

 bodily tissues on the one hand, and the respiratory 

 nerve-cells on the other, brought about by the in- 

 dependent exertion of each living factor of the 

 body in its own behalf. Every physiologist knows 

 experimentally how the whole body rises in pro- 

 test, as it were, at any interference with the free 

 performance of the respiratory functions ; and 

 that little group of cells whose business it is to 

 initiate the movements of breathing are thus pro- 

 tected from want by every part of the body, which 

 is itself dependent on them. A complete record 

 of all such co-ordinate actions would form a 

 treatise on physiology, and a consideration of all 

 the results justifies this generalization : that every 

 physiological unit of a complex organism labors 

 for its own aggrandizement alone ; but its exist- 

 ence is conditioned by an association with neigh- 

 bors, with which it must compete and upon which 

 it depends ; and this union has the suggestive re- 

 sult that every living cell in the body receives aid 



and protection from its neighbors in proportion as 

 it, in turn, by its activity, furnishes them with aid 

 and protection. 



This remarkable union of the energies of the 

 morphological elements of the body, which sug- 

 gests so clearly the social relations of an ideal 

 community, finds its explanation in the ground 

 law of the doctrine of evolution. If we but pre- 

 sume the fact of a struggle for existence among 

 the tissue-factors, the survival of the fittest must 

 be a corollary to that proposition ; and the fittest 

 individual is that whose life best tends to preserve 

 the welfare of the organism as a whole, for on 

 this depends the existence of each of its con- 

 stituent parts. 



The farther we peer into the mysteries of the 

 living animal, new utilitarian beauties are dis- 

 closed with every secret unfolded ; and the time is 

 probably not far distant when it will be difiicult 

 to point out a structure or function which, far 

 from being simply useless, has not a definite pur- 

 pose aimed at preserving the safety or perfecting 

 the economy of energy-discharge of the whole 

 body. Even if one bears in mind the well-known 

 criticism on the imperfection of the eye as an 

 optical instrument, his view would be one-sided 

 and unjust if content to rest there. The errors of 

 normal vision are nearly all errors of judgment ; 

 which is a subjective process, and it is presumable 

 that finer workmanship in the optical camera 

 would be useless in arousing sensations of greater 

 advantage to the organism. 



From a physiological point of view, the physi- 

 cal environment of an animal has only a remote 

 though a certain and most complex relation to 

 changes in the organism. Now, any change of 

 the environment must be followed by a kaleido- 

 scopic alteration in the relations of the tissues 

 among themselves, and these may be very pro- 

 found without any necessary variation of the 

 total vital configuration. Dr. Eomanes, in his 

 recent exposition concerning physiological selec- 

 tion as a means of accounting for the origin of 

 species, has done good service in looking directly 

 at the independent variable — the animal cell — 

 in seeking a solution of the intricate problem 

 presented by the body as a whole. 



If this analogy between the communal relations 

 of living cells in the body and those of individuals 

 in human society have a foundation in fact, we 

 ought to be able to use the parallel as a path of 

 research, and, from what is known concerning 

 the evolution of society, gain light as to the physi- 

 ological relation within parts of the body which 

 yield their facts very sparingly to investigation. 



A well-known physiologist has called the cen- 

 tral nervous system the final battle-ground of the 



