ON THE IDENTITY OF STRUCTURE OF PLANTS AND ANIMALS 21"] 



result will be very different. It will be found to be neither chemically 

 nor optically homogeneous, but to be composed of small definite 

 masses containing" a large quantity of nitrogen, imbedded in a homo- 

 geneous matrix having a very different chemical composition ; 

 containing in fact abundance of a peculiar substance — Cellulose. 



The nitrogenous bodies may be more or less solid or vesicular — 

 and they may or may not be distinguished into a central mass {nucleus 

 of Authors) and a peripheral portion {Contents, Primordial utricle 

 of Authors) — on account of the confusion in the existing nomenclature, 

 the Lecturer proposed the term Endoplasts for them. 



The cellulose matrix, though at first unquestionably a homo- 

 geneous continuous substance, readily breaks up into definite portions 

 surrounding each Endoplast ; — and these portions have therefore 

 conveniently, though, as the Lecturer considered, erroneously, been 

 considered to be independent entities under the name of Cells : — 

 these, by their union, and by the excretion of a hypothetical inter- 

 cellular substance, being supposed to build up the matrix. On 

 the other hand, the Lecturer endeavoured to show that the existence 

 of separate cells is purely imaginary, and that the possibility of 

 breaking up the tissue of a plant into such bodies, depends simply 

 upon the mode in which certain chemical and physical differences have 

 arisen in the primarily homogeneous matrix, to which, in contra- 

 distinction to the Endoplast, he proposed to give the name oi periplast 

 ox periplastic substance. 



In all young animal tissues the structure is essentially the same, 

 consisting of a homogeneous periplastic substance with imbedded 

 Endoplasts {nuclei of Authors); as the Lecturer illustrated by reference 

 to diagrams of young Cartilage, Connective Tissue, Muscle, Epithe- 

 lium, &c., &c. ; and he therefore drew the conclusion that the common 

 structural character of living bodies, as opposed to those which do 

 not live, is the existence in the former of a local physico-chemical 

 differentiation ; while the latter are physically and chemically 

 homogeneous throughout. 



These facts, in their general outlines, have been well known since 

 the promulgation, in 1838, of the celebrated Cell-theory of Schwann. 

 Admitting to the fullest extent the service which this theory had 

 done in Anatomy and Physiology, the Lecturer endeavoured to show 

 that it was nevertheless infected by a fundamental error, which had 

 introduced confusion into all later attempts to compare the vegetable 

 with the animal tissues. This error arose from the circumstance that, 

 when Schwann wrote, the primordial utricle in the vegetable-cell was 

 unknown. Schwann, therefore, who started in his comparison of 



