46 QUARTERLY CHRONICLE. 



110 doubt valuable account of these genera of Acari, illus- 

 trated with several plates. 



2. " Histological Researches 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 well 

 adapted for observation, since its vessels remain filled with 

 blood Avhen it is cu.t 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 Robin, and others who have demonstrated them 

 by injection. Kolliker's supposition that the perivascular 

 spaces were post-mortem products is answered by Dr. 

 Strieker's observations on living frogs. The contractility of 

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

 as likely that they w^ould have independent contractility, 

 since they are formed \iy protoplasm that simplest of elementary 

 tissues which Max Schultze, Hacckel, 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, white blood- 

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

 with the old restricted use of the word, in which it means 

 the intracellular substance merely in vegetables or embryonic 

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

 structureless, but as modified protoplasm, producing fresh 

 capillary branches by giving off" processes. Further, Dr. 

 Strieker has observed blood-corpuscles traverse, and in the 

 act of traversing, the capillary-wall, which can only be ac- 

 counted for by the hypothesis of innumerable perforations, 

 or of a jelly-like consistency, which is the view Dr. Strieker 

 takes. As to the fact of the capillary wall 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 fowl, that ca- 

 pillaries may be produced and branch out in all directions 

 from those normally existing, thus increasing greatly the 

 vascularity of a tissue. 



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

 demonstrating different 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 the finest capillary vessels 



