80 SCIENCE PROGRESS 



obeying no known physical laws, dependent from moment to 

 moment on the continuance of certain physical conditions. 

 Want of oxygen will destroy in a few seconds all the phenomena 

 of consciousness ; lack of the chemical secretion of the thyroid 

 gland will turn an intelligent child into an idiot ; a lo per cent, 

 change in the absolute temperature will destroy the labile 

 physico-chemical structure of the medium in which life works ; 

 an appropriate salt solution will cause an egg-cell to develop 

 without the intervention of a male ; and the means by which 

 the physiological activities are expressed, and the psychical 

 activities are communicated, are exclusively physical in nature. 

 Clearly the physical is a very fundamental aspect of the living 

 creature. On the other hand, it is difficult even to conceive the 

 possibility of an instrument, a mechanism, capable of being 

 designed in the physical or engineering sense, capable so to 

 speak of being described in a patent specification, which would 

 possess in the least degree either the human properties of 

 consciousness or emotion, or the powers of purposive adapta- 

 tion possessed even by the humblest living cell. To many 

 minds there is something of a different kind, not merely of a 

 different degree, in the living creature. The most funda- 

 mental, the most insoluble, the most prolific of all the problems 

 of physiology are these : where (if an5rwhere) do the physical 

 aspects of life end ? where (if anywhere) do we come up finally 

 against the fundamental biological and spiritual aspects ? 



It is notorious that all attempts to explain the whole 

 mechanism of any characteristically vital process by a physical 

 hypothesis have failed. Physical science, however, is still young ; 

 the most fundamental of its theories, the laws of motion, of 

 the conservation of energy, of the conservation of matter, 

 and our whole belief in a simple, infinite, mechanical universe 

 moving along in a steady stream of absolute time, are being 

 successfully assaulted, and shown to be nothing but accurate 

 first approximations to the truth. The concepts of physics 

 are changing, in kind, not merely in degree. Moreover, the 

 practical results, the instruments, and the achievements of 

 physical science are growing daily : technical improvements in 

 electrical instruments have opened up fields of which the 

 greatest of our fathers never dreamed. It is not reasonable, 

 then, to demand that the physics of to-day shall be adequate 

 to explain the phenomena of life. Rather should we learn 

 caution from these failures of the past, and avoid the grandiose 

 method of attack, based upon an insufficient appreciation of 

 the strength of the position occupied by the mysteries of life. 



Progress in physiology will come from adopting physical 

 methods of investigating the physical manifestations of life, 

 not from framing physical theories of things imperfectly under- 



