INJECTING SMALL VESSELS. 87 



alcohol; it is so penetrating that it becomes rapidly spread through 

 the vascular net-works. The sole inconvenience of this kind of injec- 

 tion is, that it cannot be made to distend any except most delicate 

 vessels, and that its ready penetration does not admit of distinguishing 

 between arteries, veins, and lymphatics.'' He also recommends a solu- 

 tion of caoutchouc. 



Another process, which may be termed the chemical process, was 

 published in the Comptes Remdns, 1841, as the invention of M. Doyers. 

 According to this, an aqueous solution of bichromate of potass, 1048 

 grains to two pints of water, is propelled into the vessels ; and after a 

 short time, in the same manner and in the same vessels, an aqueous 

 solution of acetate of lead, 2000 grains to a pint of water, is injected. 

 This is an excellent method, as the material is quite fluid, and the pre- 

 cipitation of the chromate of lead which takes place in the vessels 

 themselves gives a fine sulphur-yellow colour. Mr. Topping prepares 

 many fine injections in this way. 



Mr. Goadby has improved upon the process last named by uniting 

 to the chemical solutions a portion of gelatine, as follows : 



Saturated solution of bichromate of potash, 8 fluid ounces ; water, 

 8 ounces; gelatine, 2 ounces. 



Saturated solution of acetate of lead, 8 fluid ounces ; water, 8 

 ounces; gelatine, 2 ounces. 



The majority of preparations thus injected require to be dried and 

 mounted in Canada balsam. Each preparation, when placed on a slip 

 of glass, will necessarily possess more or less of the coloured infiltrated 

 gelatine (by thia is meant the gelatine colour-ed by the blood, which, 

 together with the acetate of potash resulting from the chemical decom- 

 position, may have transuded through the coats of the vessel,) which, 

 when dry, forms, together with the different shades of the chromate of 

 lead, beautiful objects, possessing depth and richness of colour. The 

 gelatine also separates and defines the different layers of vessels : the 

 arteries are always readily distinguishable by the purity and bright- 

 ness of the chromate of lead within them, while the veins are detected 

 by the altered colour imparted by the blood. 



Those preparations which require to be kept wet can be preserved 

 perfectly in Mr. Goadby's No. 2 fluid, specific gravity 1,100; the No. 1 

 fluid destroys them. 



I would recommend that the slips of glass employed for the dry 

 preparation be instantly inscribed with the name of the preparation, 

 written with a diamond ; for, when dry, it is difficult to recognise one 

 preparation from the other, until the operator's eye be educated to 



