576 DISEASES OF THE HEAD, NECK, VEINS, ETC. 



ENTRANCE OF AIR INTO VEINS. 



Air rapidly injected into a vein causes immediate death, but 

 if injected slowl)' it only causes great distress. The accidental 

 admission of air into the veins has often resulted in a fatal 

 termination, and advantage has been taken of the knowledge so 

 gained, for the purpose of destroying old or otherwise w^orthless 

 horses by this easy mode of death. An accidental admission of 

 air into a vein, causing death, may occur after bleeding ; for 

 example, if the pressure upon the jugular which is maintained 

 by the finger or vessel containing the blood be suddenly with- 

 drawn, a vacuum is formed, into which the air rushes with a 

 hissing, gurgling, or sucking sound. The animal is suddenly 

 seized with symptoms of faintness and convulsive breathing, 

 falls, and perhaps immediately dies. In other instances the 

 fatal termination is not so rapid, but a great faintness seems to 

 overcome the animal. He may fall and breathe with difficulty ; 

 a churning noise is said to be heard at the heart, the action of 

 which is extremely feeble. If the quantity of air which has 

 entered is but small, the animal may rally ; but more copious 

 entrance causes death by syncope ; in some cases there are 

 convulsions, whilst in others death seems to be due to mere 

 exhaustion. 



The mode of death is as follows : — The blood becoming 

 mingled wdth air, assumes a frothy character in the right 

 ventricle ; it is sent through the pulmonary artery, but becomes 

 more or less arrested in the pulmonic capillaries, in consequence 

 of the right ventricle being unable to overcome the mechanical 

 obstacle presented by air-bubbles in these vessels. The quantity 

 of blood transmitted through the lungs for the systemic 

 circulation grows less and less, according to theincrease of 

 obstruction and arrest of the blood in the capillaries of the 

 lungs. The suj)ply to the head is inadequate to afford due 

 stimulus to the nervous centres, and syncope results. If circu- 

 lation be not restored, this continues; tlie resj^iratory move- 

 ments then cease, and life becomes extinct; the heart last 

 failing in its action from want of its necessary stimulus — the 

 blood. 



From some experiments made by me and one of my pupils 

 (Mr. Hutcheon), it was found that some of the air w^as eliminated 



