NOVEMBEE 3, 1916] 



SCIENCE 



629 



salts in the blood-plasma, or the traces of 

 various substances supplied to the blood by- 

 other organs ; or add traces of certain other 

 substances : the reactions of the protoplasm 

 are quickly altered, and its structure may 

 be destroyed. It is evidently in active re- 

 lation with its environment at every point, 

 and one can not suspend this activity with- 

 out altering it. Even deprivation of oxy- 

 gen for, perhaps, a minute may kill a 

 nerve-cell. There is no permanent physical 

 structure in the cell: the apparent struc- 

 ture is nothing but a molecular flux, de- 

 pendent from moment to moment on the en- 

 vironment. 



Now when we look at the blood, the in- 

 ternal or immediate environment on one 

 side of the cells in the body, we find, as al- 

 ready shown, that this is almost incredibly 

 constant in composition. Were it not so 

 the reactions of the cells would become 

 chaotic, and their structure would be com- 

 pletely altered if not destroyed. But the 

 constancy of the blood is maintained by 

 the combined reactions of the organs and 

 tissues themselves. The intimate structure 

 of the living cells depends on the constancy 

 of the blood, and the constancy of the blood 

 depends on the intimate structure of the 

 tissues. If we regard this condition as 

 simply a physical and chemical state of 

 dynamic balance, it is evident that the bal- 

 ance must be inconceivably complicated 

 and at the same time totally unstable. If 

 at any one point in the system the balance 

 is disturbed it will break down, and every- 

 thing will go from bad to worse. 



A living organism does not behave in 

 this way: for its balance is active, elastic, 

 and therefore very stable. "When a dis- 

 turbance affects its structure or internal 

 environment it tends to "adapt" itself to 

 the disturbance. That is to say its reac- 

 tions become modified in such a manner 

 that the normal is in essential points main- 

 tained. An injury heals up : destroyed 



tissue is reproduced, or other parts take on 

 its function ; the attacks of microorganisms 

 are not only repelled, but immunity to fu- 

 ture attacks is produced. In reproduction 

 the body periodically proceeds to renew al- 

 most the whole of its structure. Death 

 may be regarded as a periodical scrapping 

 of structural machinery, and reproduction 

 as its complete renewal. 



The Anglo-American expedition of which 

 I was a member studied, on the summit of 

 Pikes Peak, Colorado, adaptation to the 

 want of oxygen which causes, in unadapted 

 persons, all the formidable symptoms 

 known as "mountain sickness." As adap- 

 tation proceeded the blueness of the lips, 

 nausea, and headache completely disap- 

 peared, and it was then found that even 

 during rest the lung epithelium had begun 

 to secrete oxygen actively inwards. The 

 kidneys and liver were now also regulating 

 to a lower degree of alkalinity in the blood, 

 so that the alveolar C0 2 pressure was di- 

 minished, and the breathing consequently 

 increased, thus raising the oxygen-supply 

 to the lungs. There was also a marked in- 

 crease in the hemoglobin percentage and in 

 the blood volume. The organism had so 

 adapted itself as nearly to compensate for 

 the deficiency in oxygen supply, just as a 

 heart gradually compensates for a perma- 

 nent valvular defect. 



The normals of a living organism are no 

 mere accidents of physical structure. They 

 persist and endure, and they are just the 

 expression of what the organism is. By 

 investigation we find out what they are, 

 and how they are related to one another; 

 and the ground axiom of biology is that 

 they hang together and actively persist as 

 a whole, whether they are normals of struc- 

 ture, activity, environment or life history. 

 In other words organisms are just organ- 

 isms and life is just life, as it has always 

 seemed to the ordinary man to be. Life as 

 such is a reality. Physiology is therefore a 



