Iiitroducho7i to Animal Morphology. 15 



connective tissue, cartilage, bone, cornea, dentine, &c., 

 characterized by having ovoid or branching cells in an 

 intercellular substance,* which may contain mucin, 

 collagen, chondrogen or ossein, all of which are mor- 

 phologically equivalent. In the embryo it appears as 

 a cluster of closely adpressed plastides with feeble cell- 

 walls, and is known as indifferent tissue, as its after 

 development into one or other of the series depends 

 on external influences. 



The forms of connective tissue are — ist. Cellular or paren- 

 chymatous, consisting of rounded or fusiform cellsf with a 

 sparing intercellular substance, sometimes little more than a 

 thick cell-membrane. This simple form occurs in the ectoderm 

 of Coelenterata, gland parenchyma, the notochord, &c. 2nd. 

 Mucous tissue, masses of oval, spindle, or branched cells with 

 interlacing processes, with a copious intercellular substance 

 containing mucin. This exists in the discs of Jelly fishes, Tu- 

 nicates and Heteropoda, the gelatine of the umbilical cord of 

 Mammals, &c. 3rd. Retiform or areolar, fine anastomosing, 

 sparingly or non-nucleated fibres, swollen at their junctions, 

 often with amoeboid cells in the interspaces. The connective 

 tissue of the vitreous humour of the eye, the investing reticulum 

 of absorbent glands,:]: the tunica adventitia of blood vessels, 

 neuroglia, &c., are of this sort. 4th. Blood and lymph are 

 connective tissues with a fluid intercellular substance con- 

 taining cells (see p. 32). 5th. Fibrillar tissue, cells with 

 long or reticular processes in fasciculi together with fibres 

 and coiled fibrils around each fasciculus {Slricker). The inter- 



* Which can be demonstrated by darkening it with a weak Nitrate of 

 silver solution. It is altered protoplasm as shown in bone ( Waldeyer), car- 

 tilage {Refnak and Fiirstenburg), connective tissue (Schultze and Beale). 



t As this form includes lymph cells in its interstices, it is called cytoge- 

 nous {Kolliker), or adenoid tissue [His). 



X For preserving these cells Mailer's fluid is one of the best media. It 

 consists of bichromate of potass 2^ parts, sulphate of soda, one part, and 

 distilled water, 100 parts. 



