300 Mr Treviranus on the Organic Structure 



liaders. In the following instances, he found the diameter of 

 these cylinders, and of the globules of the blood, expressed hi 

 decimals of the French millimetre, to be 



From this it appears that the diameter of the elementary cy- 

 linder is in general greater than that of the globules of the 

 blood ; I say generally, for some exceptions are mentioned, e,g, 

 the tortoise and the frog. The elementary cylinders of cellular 

 membrane are no doubt organized tubes, formed by a proper 

 tunic, and we shall hereafter see that they are of great import- 

 ance, not only being the groundwork of cellular tissue, but also 

 as forming a system continuous with the lymphatics, and proba- 

 bly extremely influential in the circulation. For some valuable 

 remarks on the microscopical observations of Mascagni, Milne 

 Edwards, and others, I must refer to the treatise itself. 



According to Treviranus, the cerebral mass, both cortical and 

 medullary, consists of hollow cylinders containing a soft pulpy 

 matter. These cylinders, extremely minute in the cortical sub- 

 stance, are somewhat larger in the medullary, and still larger in 

 the nerves. He does not determine w-hether this enlargement 

 be owing to an absolute increase of size in the same cylinders, 

 or to their being joined by other cylinders, which thus coalesce 

 into bundles ; the latter, however, he seems to think the most 

 probable supposition. In following the nerves towards their 

 periphery, he found that they have a tendency to subdivide 

 again ; and he was able to prove, that in some parts at least of 

 that periphery, the final nervous ramifications consist of cylin- 

 ders derived from a continual subdivision of the larger nervous 

 tubes into their primitive elementary cylinders. Thus in the 

 retina, Treviranus has shewn, beyond the probability of error, 

 that the following is the mode in which the nervous matter is 

 disposed : after the optic nerve has penetrated the sclerotic and 

 choroid, its cylinders or nervous tubes spread themselves out in 

 every direction, either singly, or collected into fasciculi ; each 

 single cylinder and each fasciculus, on arriving at a certain 



