Journal of Applied Microscopy. 



83 



until the mercuric chloride has been all 

 washed out; in formula (c) wash one 

 day in seventy per cent, alcohol and 

 sitore in eighty-two per cent, alcohol. 



Mammals from which demonstrations 

 of karyokinesis are most to be desired, 

 especially for medical students, are, 

 nevertheless, the most unsatisfactory. 

 The testis again, especially of rodents 

 such as the mouse, rat, or guinea-pig, is 

 perhaps most favorable. It should be cut 

 up into small pieces and fixed in Flem- 

 ming's or Hermann's twenty-four hours, 

 washed in running water several hours, 

 and hardened in the alcohols. Iron 

 Hematoxylin or safranin will again be 

 found the most satisfactory stain. The 

 mesentery of new-born rabbits has been 

 recommended as affording satisfactory 

 demonstrations of cell-division in the 

 covering epithelium. 



Likewise the amnion of the rat has been 

 advanced {| || as a good tissue for dem- 

 onstrating indirect cell-division. White 

 rats were employed and the amnion of 

 embryos, eighteen to twenty mm., were 

 fixed in strong aqueous solution of picric 

 acid (picro-acetic will do) or Flemming's 

 fluid, spread out flat on the slide, and 

 stained with hematoxylin. The karyo- 

 kinetic figures are represented as being 

 numerous and large. Neither of these 

 methods have been personally tested; it is 

 suggested that other netw-born animals, 

 e. g., kittens and the amnion of other 

 embryos, may be used with equally good 

 results. 



Cornell University. 



tlOrth, Joh. ; Cursus der normalen Hls- 

 tologie zur Elnfuhrung In den Gebrauch des 

 Mikroskopes sowie in das praktische Stu- 

 dium der Gewebelehre. 5te Aufl. Berlin, 

 1888. 



II llSolger, B. Saugethier-Mitosen im his- 

 tologischen Kursus. Arch. f. mlkr. Anat., 

 Vol. XXXIII, 1889, p. 517. 



The Use of Formalin in the Silver 

 Nitrate Method of Staining En- 

 dothelial Cells. 



G. Carl Huber, M. D. 



The following method has proven very 

 satisfactory in preparing preparations, 

 to show the endothelial cells of vessels 

 and serous membranes, for large classes. 



A small mammal (rat. Guinea-pig, 

 small rabbit or cat) is narcotized. Before 

 the heart's action is completely arrested, 

 the thorax is opened and the heart 

 incised. As soon as the blood stops flow- 

 ing, a canula is inserted and tied in the 

 thoracic aorta a short distance above 

 the diaphragm, and fifty to eighty cubic 

 centimeters of a one per cent, solution 

 of silver nitrate injected through the 

 canula. About fifteen minutes after the 



injection of the silver nitrate solution, 

 there is injected through the same 

 canula one hundred to one hundred and 

 fifty cubic centimeters of a four per cent, 

 solution of formalin (formalin ten parts, 

 distilled water ninety parts), the infe- 

 rior vena cava being cut, just before it 

 enters the heart, before the injection 

 of the formalin. The abdominal cavity 

 is then opened, loops of the intestine 

 with the attached mesentery removed, 

 and placed in a four per cent, solution 

 of formalin, in which the tissue is 

 exposed to the sunlight. As soon as the 

 reduction of the silver nitrate has taken 

 place, which is of course easily recog- 

 nized by the brown color assumed by 

 the tissues, the mesentery is divided 

 into small pieces, dehydrated first in 

 ninety-five per cent, then in absolute 

 alcohol, cleared in oil of bergamot, and 

 mounted in balsam. As a rule the 

 endothelial cells covering the two sur- 

 faces of the mesentery, and the endoth- 

 lial cells lining the arteries, veins, and 

 capillaries are clearly outlined by the 

 reduced silver nitrate. It often happens 

 that the intercellular cement between 

 the non-striped muscle cells of the ves- 

 sels is also stained, giving thus clear 

 outlines of the involuntary muscle cells. 

 If desired, the tissue may be further 

 stained in haematoxylin (we have used 

 Boehmer's haematoxylin solution) after 

 dehydration in ninety-five per cent, alco- 

 hol; after which they are dehydrated, 

 cleared, and mounted in balsam. It has 

 seemed to me that by washing out with 

 formalin what silver nitrate there 

 remains in the vessels, after the forma- 

 tion of the albuminate of silver with the 

 intercellular cement substance, the 

 brownish precipitate which is so often 

 found in the vessels after the reduction 

 of the silver, when the silver nitrate 

 method is employed as usually recom- 

 mended, is done away with. The injec- 

 tion of formalin into the vessels tends 

 also to harden them in a state of dis- 

 tention, which is an advantage. 



University of Michigan, Ann Arbor, 

 Mich., February, 1S98. 



The Microscope on a Man-o'-War. 



The compound microscope is admitted 

 to be an aid to our senses. The forma- 

 tion of a diagnosis is the result of judg- 

 ment founded on observation of the 

 case. Any agent that may extend the 

 means of observation or render such 

 more accurate is an agent of great gain. 

 On this ground we claim that the micro- 

 scope is of great importance where sick 

 are cared for, on board our men-of-war 

 as well as in hospitals and private prac- 

 tice. It is of as much value as the 



