104 



THE MICROSCOPE 



alcohol increases fluidity, and hardening in the vessels, both act as 

 a preservative.) Among the colours recommended are vermilion, 

 red lead, etc. To prepare the Colour. — Take dry colour, i vol. ; 

 glycerine, i vol. ; 95 per cent, alcohol, i vol. Grind thoroughly 

 in a mortar, keep in a stoppered bottle, and it is prepared for use 

 by simply shaking. 



Osborne's Method of Injecting the Arteries and Veins (PI. 

 XIV., Fig. i). — Two injecting fluids are employed, the first having 

 a density that will allow it to pass the capillaries easily, while the 

 second is of such a density that it will be arrested at the capil- 

 laries. The whole vascular system may be thus injected from the 

 arterial bulb. 



(i) The animal to be injected is immersed in tepid water, 

 and the heart laid bare. 



(2) The apex of the single ventricle, in the case of an 

 amphibian, or of the left ventricle, in the case of higher animals, 

 is then widely opened, and the blood allowed to flow from the 

 auriculo-ventricular aperture. 



(3) The cannula is now inserted, so that it reaches into the 

 arterial bulb, and two ligatures made at the points indicated by 

 L I and L 2. 



(4) When the body is thoroughly warmed, an ordinary red 

 or purple gelatine mass is slowly injected. The second ligature 

 having been let loose, a quantity of blood, gradually flowed by 

 the injecting mass, flows from the auriculo-ventricular opening. 



(5) When the gelatine mass runs quite clear, the second 

 ligature is fastened, and the syringe replaced by another contain- 

 ing red Plaster of Paris mass. The latter drives the gelatine mass 

 before it as far as the capillaries. When the gelatine is well 

 cooled, the animal is ready for dissection. This method can be 

 applied with considerable ease to all the smaller animals, such as 

 frogs, lizards, and pigeons, in preparation for class-work or investi- 

 gation. It must be remembered that alcohol cannot well be used 

 as a preservative, because it dehydrates the gelatine, causing it to 

 shrink and break up the veins. This difficulty is entirely obviated, 

 however, by using Wickersheimer's fluid, which keeps the injec- 

 tion for an indefinite time. 



