FOEMATION OF TISSUE. 127 



tissue and the transparent cartilaginous matrix. 

 The former does not result from the latter, nor are 

 the two kinds of tissue produced by the " differentia- 

 tion " of an originally homogeneous plasma, as some 

 have supposed, nor is the fibrous tissue the con- 

 sequence of a process of " fibrillation" occurring in 

 a previously transparent cartilage matrix. If this 

 complex tissue be studied at different periods of 

 development in specimens prepared according to the 

 method I have described, it will be found that the 

 mode of its formation differs in no essential par- 

 ticulars from that which obtains in the case of many 

 other textures which we have already considered. 

 Why some of the masses of bioplasm produce the 

 peculiar substance we know as cartilage, and others 

 give rise to that called fibrous tissue, is a question 

 which cannot be satisfactorily answered. We are 

 equally incompetent to tell why some masses of 

 bioplasm form muscle, others nerve, others epithelium, 

 and so forth. 



ISO. General considerations with reference to the 

 formation of tissue. It is very important to ascer- 

 tain if the different kinds of tissues are formed 

 according to one general principle, or if the processes 

 which lead to the production of tissues differing 

 much in structure, composition, and function, are 

 essentially different in their nature. There is good 

 reason for thinking that the conditions present exert 

 a certain influence upon the formative process, because 

 the formed material resulting varies to some extent if 

 the conditions under which its production takes place 

 be modified. But, on the other hand, it is quite certain 

 that no conceivable alteration in external conditions 

 will cause the bioplasm which was to produce muscle 

 to give rise to nerve, cartilage, or elastic tissue. And 

 yet each of these kinds of bioplasm, instead of pro- 

 ducing its characteristic formed material, might, if 

 the conditions were modified, form connective tissue 



