ZOOLOGY AND BOTANY, MICROSCOPY, E'JC. 455 



— perhaps more — also on a lantern or other grainless plate, and if this 

 is not sufficiently large repeat the process by taking another transparency 

 and re-enlarging. This may seem complicated and troublesome, but it 

 is well worth the trouble. By this method I have had prints of 1024 

 diameters and more with very great definition and clearness. Though, 

 of course, the exposure is longer for a slow and grainless plate, I 

 consider that it is compensated for by the clearness for the future 

 enlargement." 



(5) Microscopical Optics and Manipulation. 



General Theory of Image Formation in the Microscope.* — In the 

 May number (1912) of the Boletin de la Real Sociedad de Historia 

 Natural appears a review by Domingo de Orueta of a workf on the 

 above subject compiled by J. M. de Castellarnau y Lleopart. The book 

 is divided into three parts, the first of which discusses in seven chapters 

 the path of the rays in the Microscope and the dioptric properties of the 

 image. The second part deals with the genesis of the microscopic image 

 and the laws of its correspondence with the object. The subject of the 

 third part is the experimental demonstration of the theory of the forma- 

 tion of the image. The whole is preceded by a short prologue, and is 

 followed by a group of five addenda on such special topics as dioptric 

 demonstration of the law of sines. To a great extent the present work 

 is an expansion of Castellarnau's Vision Microscopica, which was pub- 

 lished in 1885, and which was very favourably noticed in our Journal. |. 

 Orueta incorporates into his review many interesting historical notes on 

 the progress of the Abbe theory. 



Optical Properties of Muscle. § — F. Vies has brought together and 

 published under the above title the results of many years' labours (1905- 

 10). The present volume represents the study of muscle in rest or in 

 extension, and might be briefly described as the statical optics of muscle. 

 A second volume is to follow in due course, and will deal with the changes 

 taking place during contraction or extension, in fact with the kiuematical 

 optics of muscle. This present work is divided into five parts, the first 

 three of which examine successively all the fundamental optical proper- 

 ties of muscle and of muscular fil^re, such as absorption, index of refrac- 

 tion, images in ultra-violet light, diffraction spectra of striae and their 

 ultra-microscopical structure. The fourth part deals with the reactions 

 of muscle in polarized light and the author's criticisms, based on a long 

 series of experiments, on Engelmann's celebrated theory as to the relations 

 subsisting between contractility and birefringence. The author has en- 

 deavoured to show that in various contractile elements (vibratory cilia, 

 flagellar, etc.) it is preferable not to admit the generality of the relation 

 enunciated by Engelmann. In the fifth part are condensed the principal 

 results which the study of muscular optics can bring to the knowledge 

 of muscular structure, and the author has essayed to utilize these results 

 in attempting a theory of striation. 



* Boletin de la Eeal Sociedad de Historia Natural (1912), pp. 289-297. 



t Teoria general de la formaci6n de la imagen en el microscopio (Madrid, 1911), 

 414 pp. (161 figs, and pis.). + See this Journal (1886) p. 335. 



§ Propri6t6s Optiques des Muscles. Paris: A. Hermann et Fils (1911), xviii. 

 and 372 pp. (many figs.). 



