30 ANA.TOMY AND PHYSIOLOGY OF 



menma^ Muctma, and Tamarmdus, wliicli are readily coloured blue by 

 iodine. According to his account amyloid dissolves in boiling water, and 

 its compounds with iodine are dissolved in water with a golden yellow 

 colour. The latter is decidedly incorrect, and in regard to the former, 

 Schleiden himself says {" £eitrage,'' i. 167), only the intermediate layers 

 were dissolved even after twelve hours boiling, and all the cellulose tissue 

 remained. 3, Vegetable Jelly; — under this name Schleiden compiiscd a 

 series of compounds, wliich chemists mention under different names fJBas- 

 sorm, Cerasin, Pectin, Gelin, (fee. J, but which he united on account of 

 their property of swelling up strongly in water and not becoming coloured 

 by iodine. He ascribed to this substance the property of gradually be* 

 coming difiriised in cold water, and believed many vegetable cells to be 

 composed of this substance, transitions from it existing on the one hand 

 (through the cells of the Fucacese) into cellulose, and on the other (by 

 many kinds of horny albumen) into amyloid. Excepting the statements 

 that cellulose is not coloured by iodine, and that there axist cells soluble 

 in water, there is no doubt of tlie correctness of the anatomical founda- 

 tions on which this theory rests. But on the other hand, there is jxist as 

 little doubt that the whole of this representation of the infinite multipli- 

 city of neutral hydrates of carbon and the distinction between them ac- 

 cording to their greater or less expansion in water, and more or less 

 facility with which they are coloured by iodine, could only be considered 

 as estlbHshed, whe. i/was proved t J the substaace o/vegetable oeUs 

 possessed this property in its pure condition, and that these differences 

 were not caused by foreign deposits. Since not only is this proof wanting, 

 but, on the contrary, the most definite evidence exists that the chemical 

 and physical properties of vegetable membranes can be modified in the 

 greatest degree by infiltrated matters, Schleiden's view is devoid of any 

 solid foundation. 



B. CELLS IN THEIR RECIPEOCAL CONNEXION. 



Leaving cut of view the lowest plants, and the spores and pol- 

 len-grains of the more highly organized, cells do not occur isolated, 

 but grown together in great numbers in connected masses ; in 

 this manner they form the so-called cellular tissue, contextus 

 eellulosus (parenchyma or prosenchyma, according as it is com- 

 posed of parenchymatous or^osenchymatous cells). 



From the structure of the cell, as a closed vesicle formed of a 

 special membrane, it follows that in cellular tissue the partitions 

 between any two cell-cavities must necessarily be composed of a 

 double membrane, and this may be readily observed in reference 

 to the secondary layers, in all thick walled cells, by means of the 

 microscope, for it is clearly seen, that the individual layers of the 

 membranes surround the cavities of the cells concentrically, and 

 that the secondary layers of the several cells are separated from 

 each other by the primary membrane. 



Observ. It is by no means so simple an affair as it seems at first sight 

 to determine the limit between two cells. Formeidy, when observers 

 were restricted to weaker and less perfect magnifying instruments, the bur- 



