ZOOLOGY AND BOTANY. MIOEOSCOPY, ETC. 661 



Schwann's slieath to nerves without the sheath at the point of union of 

 the anterior and posterior roots with the spinal cord, examined trans- 

 verse sections of the cord in the following manner : — The dorsal region 

 of a calf was chosen because the direction of the roots are more 

 perpendicular to the axis of the cord than in other parts. Segments 

 1 to 1^ cm., with the corresponding roots, were placed in a solution of 

 bichromate of ammonia, renewed two or three times during the course 

 of a year. It requires quite a year to harden cord in bichromate of 

 ammonia, but the process may be hastened by using successively bichro- 

 mate of ammonia and chromic acid, according to Deiter's method. 

 Sections were then made with an ordinary microtome perpendicular to 

 the axis of the cord, and afterwards deeply stained with picrocarminate 

 of ammonia. The sections having remained in O'l per cent, picro- 

 carminate of ammonia are too deeply stained, and the colour must be 

 removed with formic acid. This acid is of the usual strength and 

 dissolves part of the carmine, leaving the sections a rose colour. 



The decolorizing action is extremely valuable, inasmuch as it is very 

 slow, and acts unequally on certain elements which retain carmine more 

 than others. The formula for the formic acid solution is equal parts of 

 ordinary formic acid and alcohol at 36'^. In twenty-four hours the 

 sections are sufficiently decolorized ; they are then placed in absolute 

 alcohol, cleared up in oil of cloves, and mounted in balsam or dammar. 



All the nuclei of the neuroglia are admii-ably distinct, but the fibres 

 are usually quite decolorized. The axis-cylinders are rose, and not red, 

 but less decolorized than the neuroglia fibres. The neuroglia nuclei 

 are able to withstand a prolonged action of the formic acid and spirit 

 mixture, and their greater abundance in the grey matter than in the 

 white matter of the cord is strikingly shown. The neuroglia nuclei 

 may also be stained with purpurin or vp'ith Boehm's haematoxylin, 

 which, from lapse of time, has become brownish. As this stains all the 

 elements, everything but the neuroglia nuclei must be decolorized by 

 means of acetic acid diluted with an equal volume of water or of spirit. 

 A better result can be obtained from a logwood solution made from the 

 deposit from Boehm's haematoxylin. This deposit is washed with dis- 

 tilled water and dissolved in a 1 per cent, aqueous solution of alum by 

 the aid of heat, and then filtered. This solution only stains the 

 neiu'oglia, the axis-cylinders and nerve-cells remaining quite uncoloured. 



Demonstrating the Canalicular Prolongations of Bone-corpuscles.* 

 — Sig. G. Chiarugi in attempting to solve the problem of the existence 

 of protoplasmic prolongations of bone-cells in the primitive canaliculi, 

 answers the question partly on theoretical grounds, for thereby the . 

 formation of the canaliculi is explained, and partly on practical, since 

 they have already been demonstrated in the tooth. The author employed 

 the following method. 



Small pieces of fresh bone were decalcified in picro-nitric acid 

 diluted with two parts of distilled water. These were then transferred 

 to spirit, at first dilute, but afterwards gradually concentrated. The 

 sections were stained for some minutes in a one per cent, watery solution 

 of eosin, and then treated with a 3-4 per thousand solution of hydrate 

 of potash until the colour was no longer altered. In this way the 



* Bollet. Soc. tra i Cult. Sd. Med. Siena, 18S6, Fasc. viii. aud ix. Cf. Zeitschr. 

 f. Wiss. Mikr., iv. (1887) p. 490. 



1888. 2 Z 



