August 4, 1905.] 



SCIENCE. 



137 



fectly reversible, which certain experiments 

 seemed to prove, and resemble somewhat 

 the union of an alcohol and an acid which 

 combine to reach a condition of equilib- 

 rium. They assume for the toxin-anti- 

 toxin reaction the perfect applicability of 

 the Guldberg-Waage mass action formulas, 

 and for a number of relations have cal- 

 culated the value of the constant k. It is 

 interesting to note that a number of the 

 leading physical chemists have taken part 

 in the discussion. About a year ago 

 Miehaelis reviewed the subject in a long 

 article in the Biochemisches Centralblatt 

 and this has recently appeared in expanded 

 book form under the title, 'Die Bindungs- 

 gesetze von Toxin und Antitoxin.' Mieh- 

 aelis does not accept the Arrhenius work as 

 satisfactory or convincing, and points out 

 several conditions necessary for the appli- 

 cability of the mass action laws which do 

 not obtain in the cases in question; for 

 example, the mixtures are not homogeneous 

 and the degree of reversibility is extremely 

 limited, if it really exists. 



On the other hand, the doctrine of the 

 toxoids and toxons appears to explain the 

 apparent discrepancies and in certain mix- 

 tures secured in the experiments of Keyes 

 and Sachs, known to be free from these 

 bodies, the toxin and antitoxin combination 

 followed in proportions represented by an 

 almost perfect straight line. 



It remains to add that this whole discus- 

 sion can not fail to have an important in- 

 fluence on the attitude of medical men to 

 the rapidly developing physiological chem- 

 istry. The Arrhenius theory seemed to sim- 

 plify the question somewhat and make it 

 one of analogy with other well-known phe- 

 nomena. The facts more recently adduced 

 by the Ehrlich workers do not seem to 

 permit this theoretically preferable solu- 

 tion. The toxoid and toxon hypotheses are 

 necessarily chemical, however, and for the 



present may better serve in the advance of 

 investigation. J. H. Long. 



NOETHWESTEEJf UnIVEKSITY MeDICAL ScHOOL, 



Chicago, III. 



SCIENTIFIC BOOKS. 

 The Evolution of Man. By Ernst Haeckel. 

 Translated from the fifth German edition 

 by Joseph McCabe. 2 vols., 8vo. New 

 York, G. P. Putnam's Sons. 1905. 

 In the two stately and richly illustrated 

 volumes before us we have a translation of 

 the fifth edition of Haeckel's ' Anthropogenic,' 

 and coming as they do from the pen of one 

 who may now be regarded as a Nestor of zool- 

 ogy and the most vigorous exponent of the 

 historical method of investigation, they pre- 

 sent not a little interest. They profess to give 

 in their course of some nine hundred pages 

 an account of the embryological and compara- 

 tive anatomical evidence bearing on the origin 

 of man, a subject of perennial interest not 

 only to the laity, but also to professional zool- 

 ogists, since it involves the problem of the 

 origin of the vertebrates. 



The work opens with a chapter upon the 

 biogenetic law, or, as it is termed, ' the funda- 

 mental law of organic evolution,' and then 

 follow five especially interesting chapters de- 

 voted to a history of the development of em- 

 bryology and phylogeny. To these succeed an 

 extended account of the principal embryolog- 

 ical stages of the vertebrates and a discussion 

 of their significance, in which the germ cells, 

 segmentation, gastrulation, the germ layers, 

 metamerism, the fetal membranes and the de- 

 velopment of the general form of the body, 

 are all considered from the standpoint of their 

 bearings on the ancestral history. This com- 

 pleted, the author passes on to a consideration 

 of the recent representatives of the ancestral 

 stages and concludes with several chapters de- 

 voted to the phylogeny of the various organs 

 of the human body. 



It would require much space to consider 

 adequately the entire contents of the volumes, 

 and the purpose of this review will, perhaps, 

 be best served by indicating briefly the line 

 of descent which Haeckel advocates. It is es- 

 sentially the same as that presented in earlier 



