164 THE MICROSCOPIST. 



after a short time, in the same manner and into the same ves- 

 sels an aqueous solution of acetate of lead is injected. This is 

 an excellent method, as the material is quite fluid, and the 

 precipitation of the chromate of lead, which takes place in 

 the vessels themselves, gives a fine sulphur-yellow color. 



A red precipitate is obtained by iodide of potassium and bi- 

 chloride of mercury ; blue, by the ferrocyanide of potassium 

 and peroxide of iron ; &c. 



Dr. Goadby has improved upon the process last named by 

 uniting to the chemical solutions a portion of gelatine. The 

 following is his formula, originally published in the London 

 Lancet, and again in the Medical Examiner, March, 1850. 



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. 



Dr. Gr. gives the following remarks respecting this process : 

 "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 colored infiltrated gelatine (by which, he 

 alludes to the gelatine, colored 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 color. The gelatine also separates and defines 

 the different layers of vessels. By this injection the arteries 

 are always readily distinguishable by the purity and brightness 

 of the chromate of lead within them, while the veins are de- 

 tected by the altered color imparted by the blood. 



" Those preparations which require to be kept wet, can be 



