August 2, 1907] 



SCIENCE 



133 



to resist this farther fall. Thus a high 

 body temperature is a sign of a geologically 

 recent and highly specialized form, while 

 a low body temperature is a sign of a 

 primitive form. 



There may be a valuable suggestion here. 

 According to it the keeled birds are more 

 recent than the ostrich tribe, while the 

 carnivora and ruminants belong to families 

 more recent and more specialized than that 

 to which man belongs. Man adapts him- 

 self to a cold climate by means of his 

 clothes, and by use of his brains. The 

 marsupials seem to have failed to resist the 

 secular refrigeration at a still earlier date, 

 while the vast bulk of the animal kingdom 

 has submitted to the change in its sur- 

 roundings and become colder and colder 

 blooded, and all life activities slower as 

 time has gone on. The bearing of this 

 upon the relative rapidity of early evolu- 

 tion is obvious. The rate of evolution in 

 the present cold-blooded forms may be 

 vastly slower than in their hotter-blooded 

 ancestors. 



But suppose it to be true that there has 

 been a cosmic refrigeration, why should 

 life have waited for its appearance until 

 44° C. Many forms thrive at higher tem- 

 peratures, and algffi and low forms occur 

 and thrive in hot springs up to the tem- 

 perature of pasteurization (75° C). 



If 44° C. be the temperature at which 

 the line of descent of the birds left the 

 ocean and it has fallen since, there seems 

 to have been no reason why it may not have 

 been falling before, carrying all life with 

 it. Indeed, why should it not, if we assume 

 that 75° C. is but barely endurable, while 

 somewhere about 44° is the best for cell 

 life^ 



The suggestion seems altogether natural 

 and reasonable that both animal and plant 

 life originated at a temperature above 44°, 

 but that they followed the drop of the 



ocean or cosmic temperature so long as 

 thereby better and more grateful conditions 

 were secured. 



We may remark in passing that the drop 

 from 74° to 44° would not be likely to take 

 as long, perhaps not half as long, as the 

 drop from 44° to 14°, for after a body has 

 once fairly started cooling it cools more 

 and more slowly, the lower the temperature. 



2. Again, Quinton infers that the early 

 ocean had a concentration of between 7 and 

 8 parts per thousand of salts. This is the 

 concentration of the blood serum of the 

 birds, which seem to have kept the tempera- 

 ture most nearly constant, and may be sup- 

 posed to have most nearly the original con- 

 centration also 1. But beyond this analogy 

 this original concentration of about 7 per 

 thousand is supported by a series of stri- 

 king and important facts which seem to me 

 to form the strongest of all the arguments, 

 and the convincing one, indeed, for a basis 

 of truth for Quinton 's law. 



The surroundings of fresh-water fishes 

 would tend to lower the concentration. 

 They have indeed somewhat lower concen- 

 trations, between 6 and 7 parts per thou- 

 sand, but not over 8. Salt-water fishes, on 

 the other hand, have a greater concentra- 

 tion. Quinton cites no figure less than 9.3, 

 but they are always less than the present 

 ocean (35). How can we explain the di- 

 vergence of the two series from a point 

 otherwise than that the fishes, fresh-water 

 and salt, have been derived from ancestors 

 whose concentration was where the one 

 series ends and the other begins, and that 

 the sharks have had their blood grow grad- 

 ually more saline while the freshwater fish- 

 es have suffered a slight dilution of blood. 

 But this is not all. The concentration is 

 in man just about 8 parts per thousand, 

 while in cattle, whose craving for salt is 

 well known, and whose foods naturally lack 

 sodium, so that they are very likely kept a 



