148 TEE POPULAR SCIENCE MONTHLY 



metabolism of the body, it is agreed that the first law of thermo- 

 dynamics — conservation of energy or constancy of the sum of energy in 

 an isolated system — applies in every respect. Does the second law — 

 irreversible dissipation of energy in one direction — apply to such rela- 

 tively isolated (adiabatic) systems as a cell enclosed in its cell-wall or 

 the animal body encased in its integument. Does the cell or the organ- 

 ism act like a heat engine or an electric cell, dissipating its energy 

 in one direction, or is it a reversible mechanism, like a dynamo. In the 

 animal body, the food stuffs of high chemical potential, proteids, carbo- 

 hydrates and fats, are degraded and transformed into substances of low 

 chemical potential (carbon dioxide, urea and water), the energies passing, 

 as in a Carnot cycle, from a source of high potential to a sink at low 

 potential energy. The second law is operative here, but the process is 

 more economical than in a heat engine. Still more economical is it in 

 cold-blooded animals, while in green plants there seems to be an actual 

 reversal of the process, in that substances of low chemical potential 

 (nitrogen compounds, carbon dioxide and water) are transformed 

 into substances of such high chemical potentiality as carbohydrates, 

 proteids and oils. There is thus some indication that in plant cells, or 

 those organisms, like bacteria, which lie between animals and plants, 

 there is a possibility of reversal of those physical processes which take 

 place in inanimate nature. Of this we have further examples in the 

 nitrification of the soils by bacteria buried in it (without the aid of 

 radiant energy from the sun) or in the Brownian movements of 

 bacteria contained in a liquid.-^ Of the possibility of reversing the 

 second law in the human organism Lord Kelvin said that "even to 

 think of it, we must imagine men with conscious knowledge of the 

 future, but no memory of the past, growing backwards and becoming 

 again unborn, and plants growing downwards into the seeds from which 

 they sprang." This would assuredly be an extreme case, but Cushing's 

 production of sexual infantilism in dogs by partial excision of the 

 anterior lobe of the pituitary body fulfils some of these conditions. At 

 best, we can only affirm that the whole matter is transcendental, that is, 

 so far beyond our ken, since it involves an assumption of the old meta- 

 physical " vital principle," which Bergson revamps as the elan vital. 



A very complex view of the internal secretions and hormones is 

 that which connects them with the general protective mechanism of the 

 .body. The earliest to advance this view was Dr. Charles E. de M. 

 Sajous, of Philadelphia, whose treatise on the internal secretions, pub- 

 lished in 1903, has passed through six editions, and has undoubtedly 

 played a prominent part in bringing the subject to a focus in this 

 country. In relation to immunity, Sajous's main position is that the 



28 See J. Johnstone, Proc. and Tr. Liverpool Biol. Soc, 1913, XXVII., 

 1-34. 



