12 THE AMERICAN MONTHLY [January, 



Foremost and most important of all staining reagents is logwood ; it is easy 

 to prepare and use, and is equally serviceable for coloring the tissues either 

 of animals or plants ; and, moreover, the dye is absolutely permanent. 



Logwood is the popular English name given to the tree and the wood 

 oi HcEmatoxylon campechiamim^ of Central America, and the aqueous stain 

 is best prepared in the following manner : — A quantity of logwood chips is 

 macerated in cold water for forty-eight hours, the water being changed once 

 or twice during the process. This treatment removes .the tannic acid present 

 in the wood, and although a quantity of color also comes away a much 

 larger amount remains behind. Boiling water is poured over the chips, and 

 the solution is then evaporated down until a deep yellowish-brown liquid is 

 obtained. This portion is poured oft^ and when it is quite cold two or three 

 pieces of potash alum and ten per cent, of strong methylated spirit are added, 

 and the whole is well shaken up. The stain tends to become stronger by 

 exposure to the atmosphere for a few days ; it should always be filtered im- 

 mediately before use. Sections which are to be stained with logwood must 

 not contain a trace either of any acid or of alcohol ; the former would inevi- 

 tably destroy the color of the stain, and the latter would cause the dye to be 

 precipitated in a finely granular form. Chromic or nitric acid preparations 

 must, therefore, before being stained, be neutralized by passing the sections 

 through a strong solution of bicarbonate of soda, and washing them after- 

 wards in water ; and sections of tissues that have been hardened, or kept in 

 alcohol, must be deprived of any spirit which they ma}- contain by soaking 

 them for an hour in water. 



Place the objects in the extract, either diluted or undiluted, and as soon as 

 they are sufiiciently stained wash them in water, and preserve them in glyc- 

 erin until they are required. It is better, however, to mount objects im- 

 mediately after they have been stained, rather than delay the process. Log- 

 wood preparations may be mounted in glycerin, glycerin jelly, Farrant's 

 medium, dammar, or balsam ; but tissues which are to be mounted in the 

 two last-named media should be more deeply stained than for the others. 



Sections of brain and spinal cord should invariably be put through the fol- 

 lowing processes /^e/(9r6' (^t'/;/^'.y/rt///<?(/ with logwood: — 1st, thoroughly de- 

 hydrate the sections by soaking them one hour in 90"^ alcohol ; 2d, clear them 

 in oil of cloves ; 3d, place them in rectified benzine for forty-eight hours, chang- 

 ing the benzine thrice during that time ; 4th. wash out the benzine with 90% 

 alcohol ; 5th, remove the alcohol by soaking the sections in water ; 6th, and 

 finally, for fear that the benzine employed may have contained a trace of nitric 

 acid, neutralize with a solution of bicarbonate of soda ; the sections are then 

 washed and stained in the usual manner. It will be found that the nerve ele- 

 ments are stained a inch and beautiful violet, which is absolutely permanent. 



For staining tissues in bulk, previous to slicing w^ith the sliding or other 

 microtome, which produces sections altogether too thin to be afterwards put- 

 through the process of staining, Kleinenberg's alcoholic Haematoxylin is 

 specially serviceable, as its penetrating power is considerably higher than 

 that of the ordinary aqueous solution of logwood . 



(To be continued.) 



The Death of Professor Oscar Harger, at New Haven, Conn., on Nov. 6th, deprives 

 zoology of one of its most able and enthusiastic supporters. 



For many years Professor Harger has been the chief assistant of Prof. O. C. Marsh, 

 and much of the valuable palteontological work from under tlie direction of Professor 

 Marsh has come from the personal study of Prof. Harger. In addition to this, Prof. 

 Harger had attained rank as perhaps the best American authority on the systematic 

 study of isopods, in spite of delicate health for many years, and has been taken from 

 his work while still a young man. 



