TYPE OF MORBID GROWTH. 89 



that a muscle, a nerve, a gland, tfcc., is being formed, than the 

 vascular system sends a looped j^i'ocess into it, and takes posses- 

 sion of the new territory, as it were, in the name of the organism 

 as a whole. Every fresh vascular loop is an outgrowth from a 

 pre-existing loop, so that the unity and independence of the 

 entire system remain preserved. This law continues in force 

 throughout the whole course of subsequent growth, and is mani- 

 fested afresh in the adult organism whenever the occurrence of 

 morbid growth gives it an opportunity. 



Passing now to the consideration of these later stages in the 

 growth of organs, we are unhappily obliged to admit at starting 

 that our knowledge concerning them is still very defective. It 

 is only about the growth of bone that we possess adequate data. 

 The mode of growth of epithelium is a question which presses 

 for a solution. A few scattered facts are on record concerninp; 

 the growth of the muscles and tendons. The main point, the 

 central fact, which requires to be established in all these cases, 

 is the relative share in the formative processes taken by the 

 specific and functionally active elements of each organ on the 

 one hand, by the conjoint vascular and connective-tissue system 

 on the other ; the latter system, in its entirety, will henceforth 

 be termed the internal or intermediate apparatus of nutrition. 



A description of the growth of the intermediate apparatus 

 OF NUTRITION itself fomis the best introduction to a brief review 

 of these processes. As regards the most important of its constitu- 

 ent elements, the vessels, we follow Billroth in discriminating be- 

 tween three modes of vascularisation cZ^ novo (Gcfiissneubildung). 

 The 2^rimarij juode, which occurs only in the ai^ea vasculosa, con- 

 sists in a direct difierentiation of the embryonal cells into red 

 blood-corpuscles on the one hand, and the structural elements 

 of the vascular walls on the other. We can see the cells closino; 

 up along certain definite lines, to form denser cords ; those 

 axially placed next assume a red colour, and begin to move in a 

 clear fluid which collects round them ; while those at the 

 periphery, remaining stationary, eo ipso represent the vascular 

 walls. The walls of the new vessel are not indeed marked off' 

 from the surrounding parenchyma by any distinct boundary- 

 line ; on the contrary, -vve get the impression of a continuous 

 mass, through which canals are tunnelled in every direction; 

 moreover, single cells continue here and there to separate from 



