428 SUMMARY OF CURUENT RESEARCHES RELATING TO 



vessels) arises from uieseucliymatous clIIs, as is the case in many 

 iuvortebratts. 



The connective tissue is largely derived from mcseuchym, and, 

 moreover, from cells that arose primitively eitlier from cetoblasts or 

 endoblasts ; the greater portion probably from mcsoblasts of eudo- 

 blastic origin. It is certain that tlie development of the eonnectivo 

 substances has no necessary or direct causal connection with that of 

 hffiraal tissue. The notoeliord is a connective of purely e[)ithelial 

 origin. The various forms of this tissue are, on the one hand, closely 

 interrelated, and, on the other, arc in direct genetic connection with 

 various e])ithelia. 



Tlie hjemal tissue is essentially derived from cells of the meseu- 

 chym ; and arises chiefly from the visceral mesoblast, or vascular 

 layer. The phylogeuetic developmental centre of tlie blood-vascular 

 system of vertebrates is to be looked for in the two median euteric 

 vessels ; the aorta on the dorsal middle line, and the central vein, with 

 its local enlargement, the heart, on the ventral middle line. 



The further develojmieut of tissues, and their arrangement in 

 various local tissues is the result of histological ditferentiatiou ; this is 

 due to the laws of heredity and adaptation. The ontogenetic dittrrentia- 

 tion of tissues can only be understood and explained by being regarded 

 as a recapitulation of the phylogenetic division of labour of groups of 

 cells ; and affords a new proof of the validity of the fundamental law 

 of biology. 



Parietal Cells in Nerve-fibres* — After staining with saffraniu 

 Prof. A. Adamkiewicz found in transverse sections of nerve-fibres and 

 cords of the spinal marrow, within Schwann's sheaths, yellow to brown 

 coloured crescents which were sections of peculiar fusiform cells and 

 in his opinion represented hitherto unknown parietal cells, lying 

 within the nerve-fibres, distinguished by their saliranin reaction. 



New Constituent of the Blood and its Physiological Import t 

 Mr. L. C. Wooldridge describes the following method of obtaining 

 the constituent which he has lately discovered in blood ; the plasma 

 of the blood of peptouised dogs having been completely freed from all 

 corpuscular elements by means of the centrifuge, is cooled down to 

 about 0^ ; the plasma rapidly becomes turbid, and a decided fiocculcnt 

 precipitate is formed. This is the body which gives rise to the fibrin 

 ferment ; if examined microscopically the precipitate is found to con- 

 sist of a number of minute pale transparent bodies which are rounded 

 in shape, much smaller than red blood-corpuscles, and having a great 

 tendency to run together into granular masses. These peculiar 

 microscopical characters may perhaps explain the granules, blood- 

 plates, htematoblasts, &c., described by Osier, Bizzozero, Hayem, and 

 others. 



Phenomena of Contraction in Striated Muscle.:j: — The most con- 

 stant and essential bands of the elements of muscle are (1) the 



* Nature, xxxi. (1885) p. 548 (Proc. Ikilin Phy^ial. Soc, Feb. 27tl), 1885). 



t Pioc. Roy. Soc, xxxviii. (1884) pp. 69-72. 



; Arch. f. Anat. u. PJiysiol., 1885. |)p. 150-6 (4 fig.s.). 



