( 406 ) 



tlie very least 4) thickly pressed on one another, and pushes them 

 forward in its course. It shoves before it the 7'^ and S^^' , which 

 remain situated on its top, overlapping one another for the greater 

 part (c. f. fig. Ill and fig. VI). This however cannot be done without 

 a considerable stretching, especially of the 9'^' and in a somewhat 

 less degree of the 6^^. Like the first floral leaves of an opening 

 bud, on whose top are lying the 7^'' and 8^'\, the 9^^' dermatoma 

 remains situated on the caudal, the 6^'^ on the cranial side (see 

 fig. VI) to the right. Caudally the 10^^ ^.^j^([ eranially the 5'^ derma- 

 toma are staying behind like the basal floral leaves of this bud. 



The altogether different intluence, exerted on the cranial derma- 

 tomata by the growth of the extremity i]i caudal direction, will be 

 treated separately afterwards, but only the lateral portions pass on 

 the extremity. Neither the conception of Sherrington;, representing 

 the dermatomata passing as an unbroken whole on the extremity, nor 

 that of BoLK, representing their latero- ventral parts (the 7''' and 8''' 

 as a whole) moving roundabout an axis like the links of a chain, 

 are i*apable of satisfying us completely, albeit our fundamental thoughts 

 are the same, and borrowed from theirs. 



Keeping provisorily to a mechanical conception, we regard the 

 ranging of the dermatomata on the extremity as a consequence of 

 the stretching of the lateral parts, caused by an impulsi^'e force, 

 beginning to act on the middle of the seventh and eight dermatoma, 

 and operating from centrum towards periphery in a caudal direction. 



We hold it therefore not impossible that anatomy, in admitting 

 or rejecting a homology between the skin-branches of the lateral 

 intercostal nerves and those of the plexus bracchialis, may either 

 confirm or refute our conclusions. 



Chemistry. — Professor Franchdiont presents to the Library the 

 dissertation of Dr. F. M. Jaeger on: " CnjslaUognqjhlc and 

 molecular symmetry of position isomeric henzene derivatives'' 

 and gives a brief explanation of the same. 



(Communicated in the meeting of November 28, 1903). 



After MiTsCHERLiCH at the beginning of last century had discovered 

 isomorphism and Laurent some years later had pointed out certain 

 form-analogies in the aromatic substitution-products, there appeared 

 in 1870 the masterly researches of Groth on morphotropy. From 

 all this it might be surmised that, as all chemical and physical 

 properties of organic compounds depend not only on their compo- 



