CONNECTIVE TISSUE. 



147 



FIG. 



47. MEDULLARY TISSUE OF CHEST 

 HUMAN EMBRYO, FOUR WEEKS OLD. 



OF 



C, medullary tissue, probably tending toward the forma- 

 tion of cartilage of ribs ; P, medullary tissue, probably tend- 

 ing toward the formation of fibrous perichondriuin. Magni- 

 fied 600 diameters. 





In the animal organism, myxomatous tissue appears in the 

 following varieties : 



(a) Medullary Tissue, found in medulla of bone at an early 

 stage of development. The human embryo exhibits this tissue 

 in the first few weeks. 

 Plastids, either solid, 

 or granular and nu- 

 cleated, globular or 

 spindle-shaped, and 



of varying size, are 

 scattered in a scanty 

 jelly-like basis- sub- 

 stance. This sub- 

 stance, examined 

 without any re-agent, 

 looks granular with 

 lower powers of the 

 microscope, but with 

 high powers exhibits 

 a delicate reticulum, 

 which blends with 

 the delicate, thread-like offshoots from the plastids. Each field 

 of the basis-substance corresponds in size and shape to one plastid 

 or to a small group of plastids ; the earliest formations of basis- 

 substance arise from single plastids, by a chemical alteration of 

 the bioplasson liquid, without the formation of territories. (See 

 Fig. 47.) 



The medulla of bone exhibits this variety of myxomatous 

 tissue at the fourth and fifth month of embryonal life of man, 

 and in the case of pup or kitten at the corresponding stage, viz. : 

 time of birth. 



Fig. 33 represents this tissue in a chromic-acid specimen ; 

 Fig. 34, stained with chloride of gold, in order to demonstrate 

 the structure of the basis-substance. 



The plastids in medullary tissue often assume the spindle 

 shape, and here, too, we are satisfied that every field of basis- 

 substance arose from an original plastid, without formation of 

 territories. The embryonal and the medullary tissue in both va- 

 rieties are prototypes of tumors, termed " round-cell and spindle- 

 cell sarcoma" (globo and spindle myeloma). (See Fig. 48.) 



(bj Reticular Tissue. This is the next stage in the development 

 of myxomatous connective tissue. It consists of a reticulum of 



