MEDICO-BIOLOGIC RESEARCH 



vasography (Bohatirchuk) (22) or micro- 

 angiography (Bellman) (12). In this method 

 OM is injected into the blood stream and is 

 retained in the blood vessels of the whole 

 body or of a single organ for the duration of 

 the experiment. In the indirect method OM 

 is also introduced into the blood stream but 

 with this it is only transferred to some organs 

 or tissues which absorb this OM. Post mor- 

 tem coloring may also be of two kinds: (3) 

 through direct injection of 0^1, and (4) 

 through selective absorption of OM. 



Direct Vital Injection of OM. Direct 

 vital injection may be either total or local. 

 The purpose of the total vital injection is to 

 use the heart as a pressure pump for bring- 

 ing OM to the minute vessels of any desired 

 organ of the experimental animal. This 

 method seems to be the most natural way of 

 filling capillaries with OM. Accordingly, OM 

 has to mix with the blood and must not 

 cause any obstacle in the blood circulation, 

 nor shock to the animal or immediate fatal 

 effects. OM particles, if any, have to be 

 much smaller than the diameter of the 

 narrowest capillary (around 5-7 /x). The 

 greater the particles are the greater is the 

 danger of obstructing vitally important 

 capillaries with sudden death of the animal 

 resulting. One has to remember that par- 

 ticles of all OM have a tendency to stick 

 together producing an embolus of larger 

 size than one particle. 



Thorotrast is the best OM for direct vital 

 injection. It may be introduced into the 

 animals blood in quantity up to 10% of 

 its body weight. It does not irritate the 

 walls of the blood vessels and does not pro- 

 voke spasms as iodine freciuently does. 

 Thorotrast, due to the high number of 

 thorium in the atomic chart (290), produces 

 contrast images even in so weak concentra- 

 tions as 1 or 2 % (more details about thoro- 

 trast see further). 



The experiment with direct total vital 

 micro vasography proceeds as follows : 



(1) Blood is taken from the heart or aorta 



in the maximum permissible quantity 

 (Wiggers) (115). 



(2) OM is administered. It is better to take 

 out blood and inject OM by portions al- 

 though it prolongs the experiment for 1 or 2 

 minutes. 



(3) Pathological agent (cold, heat, drug, 

 etc.) is applied. 



(4) The animal is sacrificed no later than 

 5 minutes after the beginning of the experi- 

 ment. The method of killing must not cause 

 the displacement of the contrasted blood in 

 capillaries. Therefore, death has to be 

 achieved as fast as possible. Electric shock is 

 probably the best method in this case. 



(5) Desired organs are taken out and pre- 

 pared for microradiography according to 

 general rules. 



Local vital injection is much easier to 

 carry out. OM is introduced directly into the 

 artery of a desired organ (e.g. kidney, ovary, 

 etc.) and this is taken out after OM appears 

 in vasa efferentia. Much greater concentra- 

 tions of OM in the capillaries may be 

 achieved with this method than in total vital 

 injection. In addition to thorotrast other OM 

 may be used (pantopaque, urocon, etc.). 



Indirect Vital Injection of OM. This 

 examination is used to visualize the elements 

 of the reticulo-endothelial system (RES). It 

 is known that any particles, especially 

 colloidal ones, being introduced into blood, 

 if not excreted (secreted) are at first ad- 

 sorbed and then absorbed by RES cells. 



Of all opaciue media, "Thorotrast" 

 (Heyden, Germany, and an American prep- 

 aration under the same name) is mostly 

 used for this study. Thorotrast is the 

 trade name for the colloidal solution of 

 thorium dioxide. It contains from 22 to 26 % 

 thorium by volume. Negatively charged 

 particles of thorium are a few millimicrons 

 in size. Thorotrast is well tolerated by ani- 

 mals, mixes with blood perfect^, and its pH 

 is about 7.2. Another preparation of tho- 

 rium is umbrathor. It has an acid reaction 

 (pH about 2.3). It is not so well tolerated as 



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