April 7, 1910] 



NATURE 



159 



must take exception. Mr. Pumpclly's attitude with 

 regard to prehistoric chronology- is indicated by the 

 remark with which he introduces his description of 

 the sub-Glacial period in Central Asia. " Remember," 

 he says, "that while we look, in our time-perspective, 

 millenniums are as seconds." This generous and 

 imaginative method of treating the lapse of time, 

 which is no doubt a very necessary virtue in the 

 geologist, is wholly destructive of an accurate 

 chronology in archaeological study. Moreover, the 

 attempt to apply geological methods of dating to the 

 purely artificial growth of a city site is totally un- 

 scientific, and we are glad to note from a remark at 

 the end of Mr. Pumpelly's preface that he has already 

 realised the possibility of error in at least one of his 

 assumptions. Such dates as 8000 B.C., v.hich he sug- 

 gests for the beginning of the Neolithic settlement at 

 North Kurgan, or 5000 B.C., for the beginning of the 

 Copper age in South Kurgan, are wholly fanciful. 

 It is true that very early dates were at one time in 



Fig. 



-Terracotta figurines from the Copjjer Age Stratum (Culture III.) at Anau, suggesting a 

 cultural connection with Babylonia. From the South Kurgan. 



vogue, both in Eg>ptian and more particularly in 

 Babylonian archaeology ; but these are now given 

 up, and it is recognised that the earliest Sumerian 

 remains in Babylonia do not date from an earlier 

 period than the end of the fourth millennium B.C., 

 while the Neolithic remains at Susa are probably not 

 of a very much earlier period. While these facts 

 naturally affect the dates suggested by Mr. Pumpelly 

 for the cultures at Anau, they do not in any way 

 upset their relative arrangement. It is perhaps sig- 

 nificant that Dr. Schmidt nowhere mentions a date; 

 and throughout the whole work the material is pre- 

 sented in such a way that the student is in no way 

 hampered or misled. 



The success of the expedition, and the admirable 

 volumes which set forth its achievements and results, 

 are a striking testimony to Mr. Pumpelly's enthu- 

 siasm and powers of organisation, and at the same 

 time show the high scientific aims and standards 

 which inspire .American archaeological and geological 

 research at the present time. L. W. King. 



NO. 21 10, VOL. 83] 



SOURED MILK: ITS NATURE, PREPARATION. 

 AND USES. 



'T^HERE seems to be little doubt that as age 

 -■■ advances the microbial flora of the human in- 

 testine, especially of the lower portion or large 

 intestine, often undergoes a change both in the 

 number and in the character of the micro-organisms 

 present. From middle life onwards the number of 

 microbes increases, and species capable of inducing 

 putrefactive decomposition of proteins become more 

 abundant. This change can be roughly gauged by 

 making microscopical preparations of the dejecta and 

 staining by the Gram process, a selective method by 

 which certain organisms only are stained. In the 

 child's dejecta Gram-staining microbes are relatively 

 scanty and are mostly Bacillus bifidus and B. 

 acidophilus, and it is noteworthy that these are 

 lactic-acid producing bacilli. In and after middle life 

 Gram-staining forms usually become more and more 

 numerous, the Gram-staining 

 species now being principally 

 Bacillus putrificus and B. Welchii, 

 bacteria which induce marked 

 putrefactive decomposition of pro- 

 teins.' In unhealthy conditions of 

 the intestinal tract somewhat similar 

 changes or various abnormal fer- 

 mentations may occur. 



Metchnikoff- in a study of the 

 nature of senility formulated 

 the hypothesis that it is caused, 

 partially at least, by auto-intoxica- 

 tion, poisoning by the absorp- 

 tion of products derived from the 

 action of micro-organisms in the 

 digestive tract. Such poisons would 

 be the products of the putrefactive 

 decompositions brought about by 

 the micro-organisms named, and 

 also bodies belonging to the phenol 

 series which are formed by the 

 action of Bacillus coli, which is 

 always present in the intestines, be- 

 comes more and more numerous 

 from youth to old age, and which 

 also multiplies excessively in un- 

 healthy conditions of the digestive 

 tract. In seeking for some agent 

 which would combat the multiplica- 

 tion of micro-organisms in the in- 

 testine, particularly these harmful 

 forms, Metchnikoff conceived that lactic acid, which 

 has no deleterious action in the human economy, would 

 probably effect the end desired, since the growth of 

 these bacteria is inhibited by a moderate percentage of 

 this acid. Bienstock, for example, found that the B. 

 putrificus is inhibited in growth by B. coli thanks to its 

 acid-producing power, the acid formed, though small 

 in amount, being lactic acid. Simply to introduce the 

 acid as such would, however, be of little use, for it 

 would be absorbed and decomposed long before it 

 reached the large intestine. Metchnikoff therefore 

 sought for some means whereby lactic acid might be 

 formed in situ, and naturally fell back on the use of 

 lactic-acid-producing bacteria, which, if they could be 

 established in the large intestine, might there produce 

 sufficient lactic acid to inhibit the growth of the putre- 

 factive and other deleterious forms. But the problem 

 was not an easy one, for it entailed the finding of a 

 lactic acid ferment which would g^ow at body tem- 



1 Herter, " Bacterial Infections of the Digestive Tract," 1907. 

 - " On the Prolongation of Human Life." 



