10 GENERAL ANATOMY OF THE TISSUES. 



i 



importance, so far as their direct participation in the formation 

 of the tissues and organs is concerned; while, from their being 

 almost all contained in the interior of cells and from their 

 being concerned in many and most important ways in the vital 

 processes of these cells, their importance in other respects is 

 very great. 



The simple elementary parts, which at first wholly comprise 

 the commencing animal (or plant), often unite in the course of 

 development in such a manner that they lose their inde- 

 pendence and cease to exist as isolated elements. In this 

 manner compound forms arise, each of which answers geneti- 

 cally to a whole series of simple ones and which may most 

 fittingly be called the "higher elementary parts." Such a 

 coalescence has hitherto been observed with certainty only in 

 cells, and from these most of the tubular and fibrous elements 

 of the body are produced. 



§ 5. 



Formative and nutritive fluid — Interstitial substance or 

 matrix. — While in plants the elementary parts in by far the 

 majority of cases, unite directly with one another, in animals 

 there is a very wide difference ; a peculiar interstitial substance 

 which combines them, and is ultimately derived from the blood, 

 is always in a lower or more distant relation therewith. If 

 this take a direct share in the formation of the elementary 

 parts it is called " formative fluid," Cytoblastema (Schleiden), 

 from kvtoc, a vesicle, and j3Aa<rr»jjua, germ substance ; if it be 

 present for their maintenance, it is called "nutritive fluid/' 

 if it have nothing to do with either the one or the other of 

 these functions, it is called the matrix or connecting substance. 

 The cytoblastema is usually quite fluid, as in the blood, in the 

 chyle, in many glandular secretions, in the contents of glan- 

 dular follicles and in many embryonic organs; more rarely, 

 viscid and like mucus, as in the gelatinous cellular tissue of 

 embryos {vide infra), still more rarely solid, as the blastema 

 from which the villi of the chorion arise and grow. The 

 " nutritive fluid " takes the place of the formative fluid in all 

 perfect organs ; and except when it is contained in special 

 canals and cavities, as in bones, teeth and perhaps in some 

 cellular organs, is present in so small a quantity that it cannot 



