790 



SCIENCE 



[N. S. Vol. XXXVI. No. 936 



senility. Senility is that cessation of activ- 

 ities that comes when external conditions are 

 favorable. 



Then, the fact that washing away the ac- 

 cumulated waste products at intervals leads 

 to the reviving of the cell activities is consid- 

 ered to be a case of rejuvenescence and the 

 conclusion drawn that since cell proliferation 

 is more active at the end of eighty days than 

 at the beginning, a method of obtaining im- 

 mortality of the tissues has been discovered. 

 Of course the normal length of life of the tis- 

 sues used is several years, and indications of 

 actual senility could not be expected before 

 that time. The fact that the cells continue 

 actively to proliferate has no significance as 

 regards rejuvenescence, any more than the 

 healing of a wound in the skin of an aged 

 man by the normal processes of cell prolifera- 

 tion would indicate that his body was becom- 

 ing juvenile. Cell proliferation in detached 

 pieces of tissue is an expression of their in- 

 herent power of responding to form-regula- 

 tion stimuli, which in living bodies governs 

 the size and shape of the developing individ- 

 ual and even after maturity exhibits itself in 

 regeneration of lost parts, production of new 

 organs and in the processes of healing. The 

 conditions in this respect of the cells of the 

 detached piece, are evidently such as to call 

 for the highest possible manifestation of cell 

 proliferation, and this needs no other explana- 

 tion. 



The accumulation of waste products may 

 be one of the results of the primary causes of 

 senility, but even this much is not proved by 

 these experiments. 



H. M. Benedict 



University of Cincinnati 



SCIENTIFIC BOOKS 

 Die Musheln des Stammes. By Paul Eisler. 



Jena, Gustav Fischer. 1912. Pp. 715, 106 



figures, chiefly in colors. 



This volume on the muscles of the head, 

 neck, and trunk by Professor Paul Eisler, of 

 Halle, constitutes a part of the extensive 

 handbook of human anatomy now being edited 



by von Bardeleben with the cooperation of the 

 leading anatomists of Germany. It is one of 

 the most satisfactory of the series and illus- 

 trates how possible it is to make a real contri- 

 bution in a field of work which for over three 

 centuries has been as carefully cultivated as 

 has gross human anatomy. The subject is 

 considered from the purely morphological as- 

 pect, the mechanics of muscle action being 

 left for treatment in other volumes of the 

 series by Rudolph Pick. The only references 

 to the physiological aspects of the subject re- 

 late to the theoretical developmental mechan- 

 ics of the fascia, the tendons, and to a slight 

 degree, of the muscles themselves. In the 

 treatment of the various muscles of the head, 

 neck and trunk admirable brief reviews are 

 given of the various groups of muscles in 

 each region. Then there follows an accurate 

 description of each muscle of the group. The 

 drawings to illustrate the various muscles are 

 all from original sketches by the author, are 

 all excellent, and in many cases are the best 

 which have yet been made of the muscles 

 treated. The topographical relations of the 

 muscle are next considered and then the in- 

 nervation. Eisler has made numerous per- 

 sonal contributions to this latter subject and 

 gives a much fuller description of the inner- 

 vation of the muscles treated than has 

 hitherto been attempted. A brief description 

 of the blood supply is next given and this is 

 followed by an admirable summary of varia- 

 tions in structure, based not only on an ex- 

 tensive review of the literature, but also upon 

 Eisler's own long experience in the dissecting 

 room. Sometimes after the consideration of 

 an individual muscle and always after the 

 treatment of a group of muscles, the author 

 gives an excellent summary of the comparative 

 anatomy and the ontogenetic development of 

 the muscle or muscle group. From " prac- 

 tical" considerations the author has, in the 

 main, grouped the muscles according to the 

 topographical relations in the adult, although 

 he treats of the platysma with the superficial 

 muscles of the head instead of with the muscles 

 of the neck. This topographical grouping 



