After adducing the evidence of this impediment from _post-mortem_ examinations, and affirming that the blood does not flow freely through the lungs and pulmonary arteries, which are often filled and much distended with blood, it is observed--"The most interesting and conclusive evidence that arrest of blood in the lungs is the true key to the pathology of choleraic collapse, is to be found in the simple yet complete explanation which it affords of all the most striking chemical phenomena of the disease, the imperfect aeration of the blood, and the suppression of bile and urine." And again, says the learned author, "It is obvious that the stream of blood from the pulmonary capillaries to the left side of the heart is the channel by which the supply of oxygen is introduced into the system. One necessary consequence, then, of a great diminution in the volume of blood transmitted to the left side of the heart must be, that the supply of oxygen is lessened in a corresponding degree. This position, probably, will not be disputed by any one who will give the subject a moment's consideration. Nor, again, can it be denied or doubted that certain results must of necessity follow this limited supply of oxygen." * * * "The blood in cholera is black and thick only during the stage of collapse; in other words, during the stage of pulmonary obstruction and defective aeration." Again, in his explanation of the injection of the solution of soda into the veins of the suffering patient, it is affirmed, "The benefit, however, is of but short duration, for the primary cause of the impeded circulation, namely, the poisoned condition of the blood, being still in operation, * * * the stream of blood through the lungs will soon again be obstructed, and the patient thus passes into a state of collapse as profound as, and more hopeless than, before. It appears, therefore, that the hot saline injection into the veins and the operation of venesection, when it rapidly relieves, as it often has done, the symptoms of collapse, have this effect in common, that they facilitate the passage of the blood through the lungs, and thus lessen that embarrassment of the pulmonary circulation which is the essential cause of choleraic collapse. But whereas the _hot injections act_ by removing the impediment which results from spasmodic contraction of the arteries; _venesection acts_ by relieving over-distension of the right cavities of the heart, and thus increasing the contractile power of their walls."