160 MR. TOYNBEE ON THE ORGANIZATION AND NUTRITION 



in the adult healthy state ; and it appears to me, that the due action of the organs 

 into the composition of which these tissues enter is incompatible with vascularity; 

 in other words, that the presence of blood-vessels within them is a sign of disease. 



The first class, for instance, of the non-vascular tissues, comprising cartilage and 

 fibro-cartilage, is subject, from its situation in the joints, &c., to repeated concussions, 

 and to constant compression and attrition, which in these unyielding tissues would 

 necessarily be destructive of the integrity of blood-vessels. 



Those of the second class are required to be perfectly transparent for the due trans- 

 mission of the rays of light, which would be impossible if the circulation of a coloured 

 fluid were carried on throughout their substance*. 



The tissues of the third class are unceasingly exposed to friction, laceration and 

 incision ; and hence, of course, it is necessary that they should not be traversed by 

 vessels. 



In the numerous attempts which I have made to inject these tissues, I have never 

 been able to trace a blood-vessel into any one of them : on the contrary, my injec- 

 tions prove that the vessels which previous anatomists had traced no further than 

 their circumference (supposing them to be continued into these tissues, either as 

 serous vessels, or as red blood-vessels too minute for injection), actually terminate in 

 veins, without the limits of these tissues. The teriTii nations of these vessels in the im- 

 mediate vicinity of the non-vascular tissues, present certain convolutions, dilatations, 

 plexuses and other peculiarities, which differ in various parts, but in all instances 

 enable a large quantity of blood to circulate slowly in the neighbourhood of these 

 tissues, from which it may be inferred that they are subservient to the nutrition of 

 the latter ; and their existence certainly constitutes another argument against the 

 presence of vessels within them. 



All these non-vascular tissues are in structure very analogous : they all contain 

 corpuscles or cells, of which some of them are almost entirely made up ; while in 

 others, as the cornea, a few only are present. 



I am induced to ascribe to these corpuscles very important functions, and I shall 

 therefore make a few observations upon them. Schleiden has lately concluded, 

 from the researches which he has conducted, that all vegetable tissues are developed 

 from cells. Schwann has arrived at similar conclusions on the mode of development 

 of animal tissues, and he has proved, I think satisfactorily, that tissues which, when 

 perfectly formed, have a structure so different from each other as articular cartilage 

 and muscular fibre, are developed in a similar manner, viz. from cells. M. Schwann 

 ascribes to these cells, during development, a vital function, and believes that they 

 must have the power, not only of attracting, but also of chemically changing, the sub- 

 stances brought into contact with them-f-. 



* I believe that the blood discs circulate through all vessels, and Mullek allows that the existence of serous 

 vessels (viz. those carrying the liquor sanguinis only) has never been demonstrated. 



t The British and Foreign Medical Review, vol. ix. p. 523. It is to the very valuable article in this 



