A Hit-or-Miss Universe 



333 



does so as soon as the individual is 

 dead, but not during life. Recent work 

 has shown that the power of self- 

 digestion is shared by all organs and 

 tissues. What keeps it in check ? Oxy- 

 gen, probably. When the oxygen is 

 shut off, disintegration begins; and in 

 the higher animals this will occur if 

 the oxygen is absent for only a few 

 minutes. It is possible that the brain 

 cells which control respiration are par- 

 ticularly delicate and sensitive, and are 

 irreparably injured by the absence of 

 oxygen for a short time. Therefore, 

 suffocation causes the death of che 

 whole body, because the heart-beats 

 must cease after respiration does, and 

 therefore the nutritive solution which 

 the blood carries to all the cells is 

 shut off and they break down. Every 

 cell in the body of a mammal is poten- 

 tially immortal, it is now believed, but 

 they are so specialized, so dependent 

 on each other, that the destruction of 

 the nerve cells which control respiration 

 quickly entails the death of all the rest. 

 What is commonly called "life" is 

 to Dr. Loeb merely a chain of chemical 

 reactions. Death is merely the break- 

 ing of the chain, the interruption of the 



series. 



SUMMARY 



9. It may now be useful to sum up 

 the doctrine of the book in Dr. Loeb's 

 own words. 



"It is generally admitted that the 

 individual physiological processes, such 

 as digestion, metabolism, the produc- 

 tion of heat or of electricity, are of a 

 purely physicochemical character; and 

 it is also conceded that the functions of 

 individual organs, such as the eye or the 

 ear, are to be analyzed frcm the view- 

 point of the physicist. When, how- 

 ever, the biologist is confronted with 

 the fact that in the organism the parts 

 are so adapted to each other as to give 

 rise to a harmonious whole; and that 

 the organisms are endowed with struc- 

 tures and instincts calculated to pro- 

 long their life and perpetuate their 

 race, doubts as to the adequacy of a 

 purely physicochemical viewpoint in 

 biology may arise. The difficulties 

 besetting the biologist in this problem 



have been rather increased than dimin- 

 ished by the discovery of Mendelian 

 heredity, according to which each 

 character is transmitted independently 

 of any other character. Since the 

 nimiber of Mendelian characters in 

 each organism is large, the possibility 

 must be faced that the organism is 

 merely a mosaic of independent heredi- 

 tary characters. If this be the case 

 the question arises : What moulds these 

 indeoendent characters into a harmoni- 

 ous whole? 



■"The vitalist settles this question by 

 assuming the existence of a pre-es- 

 tablished design for each organism and 

 of a guiding force or principle which 

 directs the working out of this design. 

 Such assumptions remove the problem 

 of accounting for the harmonious char- 

 acter of the organism from the field of 

 physics or chemistry. The theory of 

 natural selection invokes neither design 

 nor purpose, but it is incomplete since it 

 disregards the physicochemical con- 

 stitution of living matter about which 

 little was known until recently. 



"In this book an attempt is made to 

 show that the unity of the organism 

 is due to the fact that the egg (or 

 rather its cytoplasm) is the future em- 

 bryo upon which the Mendelian factors 

 in the chromosomes can impress only 

 indi\'idual characteristics, probably by 

 giving rise to special hormones and 

 enzymes. We can cause an egg to 

 develop into an organism without a 

 spermatozoon, but apparently we can- 

 not make a spermatozoon develop into 

 an organism without the cytoplasm of 

 an egg, although sperm and egg nucleus 

 transmit equally the Mendelian char- 

 acters. The conception that the cyto- 

 plasm of the egg is already the embryo 

 in the rough may be of importance also 

 for the problem of evolution since it 

 suggests the possibility that the genus- 

 and species-heredity are determined by 

 the cytoplasin of the egg, while the 

 Mendelian hereditary characters can- 

 not contribute at all or only to a limited 

 extent to the formation of new species. 

 Such an idea is supported by the work 

 on immunity, which shows that genus- 

 and probably species-specificity are 

 due to specific proteins, while the 



