REVIEWS 173 



Contemporary and earlier works are freely quoted and a very complete 

 bibliography is appended. The illustrations are of a high standard, but the 

 identification of (£), fig. 25, requires further explanation than it receives in the text. 



T. B.J. 



The Elementary Nervous System. By G. H. Parker, Sc.D., Professor of 

 Zoology, Harvard University. [Pp. 229, with 53 illustrations.] (Phila- 

 delphia and London : J. Lippincott Company. Price $2.50 net.) 

 THIS is the second of thirteen monographs on Experimental Biology to be issued 

 under the editorship of Prof. J. Loeb of the Rockefeller Institute and his two 

 colleagues, but of which only two volumes have hitherto been published. 

 Dr. G. H. Parker, the author, is a well-known worker and writer in this field, 

 and the high reputation of the Editors is an assurance that the volume will be 

 appreciated as supplying a need. 



The author suggests that, as the dependence of human affairs is so absolute 

 upon the nervous system, there is a place for a work describing its earliest 

 appearance in the simplest and most elementary forms of animal life. He points 

 out that the activities of the simpler animals are often interpreted in terms of 

 human experience, and his researches based upon experimental and quanti- 

 tative investigations, rather than upon observation and inference, are designed 

 to give a description of the nervous system as it actually is rather than as it is 

 believed to work. 



Human beings have often been likened to mere strands in the web of all living 

 things, and we have need to know comparative physiology — as well as pathology — 

 before we can speak authoritatively upon conditions that appertain to ourselves ; 

 for, as is well known, parts of the nervous system that are apparently useless 

 and vestigial in man subserve important functions in lower creatures, and conditions 

 that are rudimentary or morbid in man may be normal in the lower animals. For 

 instance, cancer is almost unknown in wild animals, whether free or in captivity, and 

 atheromatous changes in the arteries, which are conditions sequential upon 

 advancing years in man are unknown in animals, even the oldest ; nor is the 

 condition described as phlebitis met with in animals, neither are rabbits nor 

 pigeons affected by even large doses of morphia. Therefore, any reliable records 

 of structural dispositions, especially if relating to the nervous system in rudi- 

 mentary forms of animal life, tend to throw light upon and to assist in the 

 explanation of functions in human beings, and this work is an endeavour to 

 simplify the intricacies of the nervous system in man by unravelling its earliest 

 phases in the lower forms of life. 



All fully developed nervous reactions require for their execution a receptor, an 

 afferent conductor, an adjustor, an efferent conductor and an effector. In the 

 lowly multicellular Spongidae there is no trace of a nervous system. The work 

 under review begins with observations upon the type Stylotella as a representative 

 of this class, and interesting experiments demonstrate the fact that the water 

 currents through the pores of the Spongidae are not due to the flagellated 

 epithelial cells lining the canals, but depend upon the controlling power exercised 

 over the closing or opening of the pores of the osculum, which is effected by the 

 sphincter band of cells on the canal walls ; this, in the opinion of the author, being 

 the prototype of involuntary muscular fibres that are the primitive elements of a 

 neuro-muscular mechanism, the elementary muscular substance acting as the 

 effector, yet itself being merely nerveless, irritable protoplasm. As this proceeds in 

 development the next stage is the appearance of a receptor apparatus to be found 



