46 QUARXERLY CHRONICLE. 



no doubt valuable account of these genera of Acari, illus- 

 trated Avitli several plates. 



2. " Histological Researciies on the Genesis and on the 

 Structure of the Capillaries,^^ by Dr. Strieker, of Vienna, 

 notice by M. Ominus. 



Dr. Strieker, from investigations on the capillaries of the 

 tadpole and frog, is led to very interesting results. The 

 nictitating membrane of the frog was found very Avell 

 adapted for observation, since its vessels remain filled with 

 blood when it is cut away, and it is easy to see the walls of 

 the capillaries. Dr. Strieker maintains that there are peri- 

 vascular spaces around the capillary vessels, confirming the 

 opinion of Eobin, and others who have demonstrated them 

 by injection. Kolliker's supposition that the perivascular 

 spaces Avere post-mortem products is answered by Dr. 

 Strieker's observations on living frogs. The contractility of 

 the Avails of the capillaries was observed also, and it is urged 

 as likely that they would have independent contractility, 

 since they are formed hy protoplasm that simplestof elementary 

 tissues Avhich Max Schultze, Haeckel, and Briicke have de- 

 scribed as essentially a contractile substance. M. Ominus 

 remarks that protoplasm, used in this sense, viz., as forming 

 the moving substance of diatoms, mycetozoa, Avhite blood- 

 cells, and sarcode more or less, must not be confounded 

 Avith the old restricted use of the Avord, in which it means 

 the intracellular substance merely in vegetables or embryonic 

 animals. The capillary Avail is then not to be regarded as 

 structureless, but as modified proto]3lasni, producmg fresh 

 capillary branches by giving off processes. Further, Dr. 

 Strieker has observed blood-cor]Duscles traverse, and in the 

 act of traversing, the capillary-Avall, Avhich can only be ac- 

 counted for by the hypothesis of innumerable perforations, 

 or of a jelly-like consistency, A\-hich is the vieAV Dr. Strieker 

 takes. As to the fact of the capillary Avail being penetrated 

 and traversed by blood-corpuscles, he is confirmed very fully 

 by his pupil M. Prussak. Dr. Strieker has observed in 

 studying inflammation in the brain of the foAvl, that ca- 

 pillaries may be produced and branch out in all directions 

 from those normally existing, thus increasing greatly the 

 A'ascularity of a tissue. 



The use of injections of nitrate of silver is interesting, as 

 demonstrating difterent chemical properties in this and that 

 part of the capillary vessels, but cannot. Dr. Strieker be- 

 lieves, be considered as indicating any particular embryo- 

 logical development. 



Dr. Strieker then concludes that tlie finest capillary vessels 



