RECONSTRUCTION BY MEANS OF WAX PLATES. 55 



Organs injected with carmin are fixed in alcohol and should not 

 be brought in contact with acids or alkalies. Such parts as are injected 

 with Berlin blue are less sensitive in their after-treatment. Pieces or sec- 

 tions that have become pale regain their blue color in oil of cloves. 



If objects or sections injected with Berlin blue be treated with 

 a solution of palladium chlorid, the bluish color changes to a dark 

 brown which afterward remains unchanged (Kupffer). 



By means of the above injection methods other lumina can be 

 filled, as, for instance, those of the glands. As a rule, these are only par- 

 tially filled, since they end blindly, and their walls are less resistant and 

 may be damaged by the pressure produced by the injection. 



Silver Nitrate. In thin membranes and sections the vessel-walls can 

 be rendered distinct by silver-impregnation, which brings out the out- 

 lines of their endothelial cells. This may be done either by injecting the 

 vessel with a i % solution of silver nitrate, or, according to the process 

 of Chrzonszczewsky, with a 0.25% solution of silver nitrate in gelatin. 

 This method is of advantage, since, after hardening, the capillaries of the 

 injected tissue appear slightly distended. Organs thus treated can be 

 sectioned, but the endothelial mosaic of the vessels does not appear defi- 

 nitely until the sections have been exposed to sunlight. 



The injecting of lymph -channels, lymph -vessels, and lymph- 

 spaces is usually done by puncture. A pointed cannula is thrust into 

 the tissue and the syringe emptied by a slight but constant pressure. The 

 injected fluid spreads by means of the channels offering the least resist- 

 ance. For this purpose it is best to employ aqueous solutions of Berlin 

 blue or silver nitrate, as the thicker gelatin solutions cause tearing of the 

 tissues. 



Altman's Process. To bring out the blood capillaries and the 

 lymphatic channels, Altman's process (79), in which the vessels are in- 

 jected with olive oil, is useful. The objects are then treated with osmic 

 acid, sectioned by means of a freezing microtome and finally treated with 

 eau de Javelle (a concentrated solution of hypochlorite of potassium). 

 By this process all the tissues are eaten away, the casts of the blood-vessels 

 remaining as a dark framework (corrosion) . The manipulation of these pre- 

 parations is extremely difficult on account of the brittleness of the oil casts. 

 For lymph-channels Altman (ibid,} used the so-called oil-impregnation. 

 Fresh pieces of tissues, thin lamellae of organs, cornea, etc., are placed 

 for five to eight days in a mixture containing olive oil i part, absolute 

 alcohol y z part, sulphuric ether ^ part (or castor oil 2, absolute alcohol 

 i, etc.). The pieces are then laid for several hours in water, where 

 the externally adherent globules of oil are mechanically removed and 

 those in the lymph-canalicular system are precipitated. The objects are 

 now treated with osmic acid, cut by means of a freezing microtome, 

 and corroded. In this case, the corrosive fluid (eau de Javelle) should 

 be diluted two or three times. 



RECONSTRUCTION BY MEANS OF WAX PLATES. 



It is often impossible to obtain a clear conception of the form of minute 

 anatomic structures, nor of their relations, by means of sections or by the 

 methods of maceration and teasing. To obviate such difficulties methods of 

 reconstruction have been devised, by means of which such structures may 

 be reproduced in an enlarged form without losing their inherent morpho- 



