Chemistry and Physics. 541 



its predecessors in the diversity of topics which it presents. It 

 is impossible to make special mention of more than a few of the 

 papers. Particularly noteworthy are the valuable studies of 

 Embden and his collaborators on the formation of acetone in the 

 liver, indicating a Targe number of substances as possible pre- 

 cursors of this compound. Friedmann's renewed investigation of 

 the structure of adrenalin leads to a choice of the formula 



OH / \ CH(OH)CH -NH-CH, 

 OH M 



for this peculiar physiological compound, the formation of which 

 Halle, in a separate paper, refers to an enzymatic reaction of the 

 suprarenal tissue upon tyrosin. Among a series of contributions 

 from the laboratory of Dr. von Ftirth, reference may be made to 

 his study of chitosan derivatives. It indicates that the "chitin" 

 of molluscs and arthropods furnishes the same products. Two 

 papers offer items of interest regarding nitrogenous metabo- 

 lism : one by H. Vogt deals with the time relations in the cata- 

 bolism of proteids of various groups ; the other, by Klercker, 

 gives evidence that creatine and creatinine may experience quite 

 different fates in the chemical reactions to which they become 

 subject in nutrition. The volume also contains the usual number 

 of papers on enzymes : rennin, diastase, gastric lipase, and the 

 blood enzymes furnishing the themes for investigation, l. b. m. 



7. Change of Colloidal Nmleation in wet dust-free Air in the 

 lapse of time y by C. Bartjs (Communicated). — Observations 

 extending over several months have now shown that the variation 

 of the colloidal nucleation of dust free wet air in the lapse of 

 time is independent (within the limits of accuracy of the fog 

 chamber) of the barometric pressure and temperature of the 

 atmosphere, of the ionization of the air or of the allied effect of 

 natural external radiations ; but that it varies to the remarkable 

 extent of an increase of about 8000 nuclei per rise of temperature 

 of one degree centigrade near 20 degrees. The reason for this 

 unexpected result is yet to be found, but nothing has been sug- 

 gested to explain it away. 



Brown University, Providence, E. I. 



8. Leitfaden der x jra ^tischen Optik ; von Dr. Alexander 

 Gleichen. Pp. viii + 221; 158iigures. Leipzig, 1906 (S. Hirzel). — 

 This is an account of the more elementary parts of the theory of 

 optical instruments, and is intended for the users of such instru- 

 ments rather than for the optician or for the reader who is 

 interested in the more complex details of geometrical optics. It 

 is written in a clear and simple manner and no mathematics is 

 used beyond the elements of geometry and algebra. Especial 

 attention is given to the optics of the eye and of photographic 

 apparatus, and the book will doubtless prove especially useful to 

 oculists and photographers. h. a. b. 



Am. Jour. Sci. — Fourth Series, Vol. XXII, No. 132. — December, 1906. 

 37 



