867 



woman, therefore, as /^^s y^ />o.28 qj. po.56^ jjjyj ^^^ between iionio- 

 nenric species. 



hi function of the muscle weight, however, the brain weight in 

 every species — also in the human species — between individuals 

 of equal and of ditferent sexes, varies proportionally to jIP^b 



This is different between homoneuric species. For them the brain 

 weiffht varies both proportionally to M^-^^ and to /-'oös. in propor- 

 tion to the weiyht or volume of the muscles (he brain weight increases, 

 therefore, more than within a species. 



Here an important difference in the relation between homoneuric 

 species and between the two sexes — also in the human species — 

 becomes apparent, with which without doubt differences in the 

 anatomical and physiological relation of the nervous system and the 

 njuscular system are connected. 



In fact it has already long been known that the muscle fibers of 

 man are on an average considerably thicker than (hose of woman. 

 Bowman ') found (already in 1840) that the mean diameter for 

 man is about a fourth larger, corresponding to a ratio of the area 

 of the sections of 1.664. Schwalbe and Maykda') lay great stress 

 on the "bedeutenden Einfluss", which the sex has on the thickness 

 of homologous muscle fibers. "Ganz algemein liegen in den 

 hier verwerthbaren Messungen die Kaliber-Maxima im weiblichen 

 Muskel tiefer als iir) maimlichen" (p. 502). Tiie same sexual differ- 

 ence holds for the average calibers of the comparable measurements, 

 represented in Table VI. So also for the relative widths and maxima 

 of the "curves of variation", from which appears perfect uniformity 

 of these mean curves (for the width as well as for the maxima the 

 ratio is 1.653); which in connection with the functional relation 

 between the nerve and the muscle found by Kkith Lucas, [Mtnes, 

 and b}' Lapicque in their researches, is of great importance. ') 



The average area of section of the fibers of these three muscles 



1) W. Bowman, On the Minute Structure and Movements of Voluntary Muscle. 

 Philosophical Transactions of the Royal Society of London for the year 1840. 

 Part II, London 1840, p. 46L 



2) G. Schwalbe und R. Mayeda, Ueber die Kaliberverhaltnisse der querge- 

 slreiften Muskelfasern des Menschen. Zeitschrift fur Biologie (Kühne und Voit). 

 Band 27, München und Leipzig 1890, p. 482—516. 



3) K. Lucas, in Journal of Physiology. Cambridge 1905, p. 125; 1909, p. 113. - 

 G. R. Mines, Ibid. 1913, p. 1. — L. Lapicque, in Comptes rendus de la Société 

 de Biologic. Paris 1913, p. 35. — The fibers of a skeleton muscle can, namely, 

 each of them separately gel into contraction. Without doubt this must be in con- 

 nection both with the thickness of the muscle fibers and with the thickness of the 

 nerve fibers. 



