ARRANGEMENT OF STRUCTURAL ELEMENTS. 221 



Numerical relations in the architecture of the central 

 system are still to be examined, and to these we next 

 turn. Under the title of " The number and distribution 

 of the medullated fibres in the spinal cord of the frog," 

 Gaule T has published some interesting observations. 

 His view of the animal organism, metaphorically 

 expressed, is that of a complex organic molecule. In 

 such a molecule the cell elements of the different tissues 

 are assumed to stand related to one another as do the 

 atoms in the molecule of the chemist. This conception 

 involves the idea that a given number of one group of 

 elements demands a corresponding number of another 

 group. The application of this notion to the spinal 

 cord of the frog is as follows : A certain number of 

 afferent and efferent fibres connected with the cord 

 requires within it a corresponding number of cells and 

 fibres, which shall put the segmental elements in con- 

 nection with one another and with the higher centres. 

 From the previous investigations of Birge there were 

 records of the number of nerve fibres in the spinal nerve 

 roots of the frog, and these records form one basis for 

 the subsequent calculations. According to Gaule's 

 theory each root fibre, both ventral and dorsal, has 

 usually eleven connections, which in certain localities 

 determined upon may be reduced to a smaller number. 

 By this expression is meant that in the cross-section of 

 the spinal cord there will be found eleven fibres for each 

 fibre found in the roots. To test this hypothesis Gaule 

 made cross-sections of the spinal cord ; (i) just at the 

 point where it passes into the bulb ; (2) through the 

 middle of the cervical enlargement ; (3) in the upper 

 half of the thoracic region ; (4) through the upper 

 portion of the lumbar enlargement ; (5) through the 



1 Gaule, Abhandl. d. ]\fathemat,-Physiol. Cl. Konigl. Sachs 

 Gesellschcift der Wissenschaften, 1889. 



