PULMONARY ARTERY. 521 



left ventricle, and firmly tied there by a strong ligature ; the cork should have a trans- 

 verse notch for the reception of the lisutnre. 



Instead of injecting by the carotid, a long curved canula may be fixed to the aorta 

 itself, after making an opening in the left side of the chest, on a level with the heart, 

 by the ablation of two segments of the ribs, and incising the pericardium and left 

 auricle to introduce it. This mode allows the tallow to be injected at a very high 

 temperature, and gives the best results, lor it can then penetrate to the capillaries, if wb 

 only know how to manage it ; in certain organs the injected matter may even be made 

 to return by the veins. 



But no matter what procedure may be adopted, there are several parts into which 

 the tallow can never be made to enter by a general injection ■ tliese are the four extre- 

 mities. So that a special operation must be resorted to, in order to fill their vessels. 

 After separating them from the trunk, by sawing them through aliove the knees and 

 hocks, they sliould be allowed to steep for two houis in water, constantly kept up to a 

 temperature of 140° to 160" Fahr. !it mo»t ; it is then easy to inject them, either by the 

 posterior radial artery, or the- anterior tibia!, alter tying those 'branches which may be 

 open at the cut extremity of the limbs. 



If it is desired to make partial injections in other parts of the body, it will be better 

 not to separate them from the trunk ; but only to tie those vessels which anastomose 

 between the arteries to be filled and those which are not. For example, to inject the 

 arteries of the head, it suffices to push the mixture into one of the common carotids, 

 after ligaturing the other in the middle of the neck, and both vertebrals in the space 

 between the two portions of the scalenus muscle. 



We may give the tallow more fluidity, and a higher degree of penetration, by mixing 

 ■with it a little spirits of turpentine ; or more consistence, in adding to it a small proportion 

 of beeswax. 



The two following mixtures are borrowed from Cruveilhier's Anatomy : — 



Tallow 9 parts 



Turpentine 1 „ 



Ivory Black, mixed with spirits of turpentine . 2 „ 



For preservative injections : — 



Beeswax 1 part 



Tallow 3 „ 



Vermilion, indigo, or Prussian blue, previously 

 mixed in spirits of turpentine A suificient quantity. 



Of course it is well understood that these instructions are only intended for the 

 dissecting-room injections necessary for the study of descriptive anatomy. To inject the 

 c'apillaries, it is requisite to have recourse to other substances and other procedures. 

 Suffice it to say that these injections are made with cold fluids, such as varnish, alcohol, 

 or spirits of turpentine, holding in suspension extremely fine colouring matter, gum arable 

 dissolved and coloured by a substance also in solution, etc., or, better still, colours 

 rubbed up in oil, and mixed with spirits of turpentine. 



Dissection of the arteries. — There are no general rules to be given for the dissection 

 of arteries. 



CHAPTEE II. 



PULMONAKY ARTERY (Fig. 258, e). 



Preparation. — The pulmonary arteiy is not filled by the general injection mentioned 

 above. It is directly injected by propelling the tallow into the right heart by the 

 anterior vena cava, after tying the posterior vena cava. 



The pulmonary artery springs from the infundibulum of the right 

 ventricle, is directed upwards and then backwards, describing a curve whose 

 concavity is infero-posterior, and arrives above the left auricle, where it 

 divides into two secondary arteries, one for each lung. These arteries 

 enter the pulmonary tissue with the bronchi, and exclusively ramify in it. 



The pulmonary artery accompanies the trunk of the aorta on the right 

 side, and is envelopefl with it in a serous sheath, a dependency of the visceral 

 layer of the pericardium. At its origin, it is flanked before and behind by 



