Journal of Applied Microscopy. 



are also admirably brought out. Tbe 

 capillary and arteriole also offer remark- 

 ably good opportunity for the beginner, 

 for the nueleui of the endothelium in 

 both, and those of the un-striped muscle 

 tissue in the arteriole are superbly 

 shown, and the relations of the vessels, 

 their relative sizes, and such points, are 

 well given. I hardly know of a more 

 available method for getting vascular 

 tissue for simple elementary study. 



h 



— iz- — 



The advantage whi'ch this method 

 offers is its ready and quick a.pplication. 

 All other isolation methods, as of soak- 

 ing in weak alcohol, involve at least one 

 day, if not several days, of preparation, 

 while with this method one can use ma- 

 terial obtainable on the spur of the mo- 

 ment and complete the process inside of 

 a couple of hours. Like all rough and 

 ready methods, it has its drawTDacks; 

 still, considering the distance it takes 

 one on the road to a complete knowledge 

 of the nerve ganglion cell, I think it de- 

 serves consideration. 



Biological Laboratory, Hamline Uni- 

 versity, Dec. 11, 1897. 



Agar. 



As the process of making agar given 

 in text books on bacteriology and bacte- 

 riological technique is unnecessarily te- 

 dious, and as it not infrequently happens 

 thkt precipitates make their appearance 

 in the tubes after sterilization, although 

 the product appeared to be clear when 

 filtered and run off into the tubes, a 

 modification of the process which obvi- 

 ates the formation of secondary precipi- 

 tates and at the same time lessens the 

 time required for making agar, will 

 doubtless be of interest to those who 

 still employ the old process. After num- 

 erous efforts to devise a satisfactory 

 method, I have finally adopted the fol- 

 lowing, by whidh a very clear agar, in 

 which no secondary precipitates appear, 

 can be made in a comparatively short 

 period, the whole process if properly 

 manage'd being completed within two- 

 and-a-half to three hours: 



Pour a liter of water over a pound of 

 finely minced lean beef and allow it to 

 simmer over a slow fire for half an hour; 

 then boil for fifteen minutes and filter 

 through paper. Rub up ten grams of 

 powdered agar in a little cold water, 

 gradually adding more water until all 

 of the powdered agar has been moist- 

 ened and the mixture made thin enough 

 to readily pour out of the dish (consist- 

 ency of thin mucilage); stir this into the 

 filtered meat-infusion and place it on 

 the fire to boil in a porcelain lined sauce- 

 pan. In like manner rub up five grams 

 of sodium chlorid, and ten grams of 

 Witte's peptonum siccum (dry peptone), 

 in a little cold water and stir this into 

 the mixture; boil until the agar and pep- 

 tone are dissolved, which requires usu- 

 ally about ten minutes; now remove from 

 the fire and carefully neutralize, prefer- 

 ably with caustic soda; make up the bulk 

 to one liter and transfer to flasks. The 

 flasks are now placed in the steam ster- 

 ilizer, sterilized for twenty minutes and 

 then allowed to remain in the sterilizer 

 with the flame turned low until the pre- 

 cipitate thrown down by heat and the 

 insoluble particles have separated and 

 subsided; the clear supernatent fluid 

 agar is now syphoned or carefully poured 

 off and run into tubes, while the turbid 

 portion is reheated to the boiling point, 

 preferably in the steam sterilizer, and 

 filtered through folded filter paper, of 

 coarse mesh, which has just been moist- 

 ened with boiling hot water. Should the 

 clear portion become slightly clouded by 

 inadvertantly pouring a little of the sedi- 

 ment into it so as to require filtration, 

 it will be necessary to reheat this also 

 before attempting filtration; but it is 

 best to keep it separate from the more 

 turbid portion as it will filter much 

 more rapidly, being comparatively free 

 from flocculi, the tendency of which is to 

 clog the filter. 



By this method the use of the white of 

 egg for clarifying is rarely if ever nec- 

 essary, and if proper filter paper is used 

 filtration is quickly and readily accom- 

 plished without the use of hot water 

 funnel or other means of keeping the 

 mass hot. It is the sterilization and 

 spontaneous separation of the coagulated 

 and insoluble particles (including the 

 phosphates thrown down by heat) which 

 obviates the appearance of secondary 

 precipitates and does away with the 

 necessity of clearifying, while the de- 

 cantation of the larger part of the mass, 

 which has thus become perfectly clear, 

 reduces the bulk of the mass requiring 

 filtration to such an extent as to enable 

 the turbid portion to run through the 

 filter before it has had time to oool 

 enough to thicken in the filter. 



The process can be still further short- 



