60 



THE COMPOSITION OF EXPIRED AIR. 



Post-mortem examinations of a number of the animals dying in the " Brown-Scquard " experi- 

 ments were made with the greatest care. 'J'he organs were preserved in alcohol and mounted in 

 celloidin for the microscopic examination. The gross appearances presented by the animals showed 

 a constant similarity to the appearances noted in the animals used in the experiments with artificial 

 gaseous mixtures. The constant appearances noted were those of intense venous engorgement of 

 all the organs and tissues. The heart cavities contained firm, dark clots of blood, filling both 

 auricles and ventricles, those on the right side being usually much larger than those on the left. 

 No inflammatory changes or serous exudates were found in any instance. 



Microscopic examination of the organs presented no constant feature aside from the manifesta- 

 tions produced by the cause and mode of death. Engorgement of the blood vascular system was 

 noted everywhere with usually some degree of infiltration in the lung. No degenerative changes 

 were constantly present. Those found in isolated cases — such as a slight increase of connective- 

 tissue elements between the tubules of the kidneys and about the glomeruli, and small areas of 

 proliferation of connective-tissue elements in the liver — cannot be safely attributed to the experi- 

 ment. This opinion is strengthened by the short duration of the experiments, and it is probable 

 that the changes were due to ante-experimental causes. 



The mode of death as observed in these experiments presented certain constant features which 

 were undisiinguishable from those produced by slow asphyxia under other circumstances. There 

 was a period of excitement, followed, in the course of time, by a period of progressive depression. 

 The breathing, at first rapid, generally became slower, with perceptible lengthening of the respiratory 

 pauses, accomjjanied at a later period by marked expiratory efforts. Along with these respiratory 

 changes was usually noted a progressive muscular weakness gradually deepening into paralysis of 

 the posterior members. The animal moves about with evident difficulty, and finally sinks down, 

 remains lying on the side or back, without any other movements than those of respiration. It now 

 presents a comatose condition from which it cannot be aroused by striking the sides of the bell jar. 

 Death usually ensues through the gradual lengthening of the respiratory pauses passing into an 

 entire failure of respiration. In a small proportion of the cases, life becomes extinguished through 

 one or two convulsive seizures. 



No. I. Brown-S^quard Experiment. 



Commenced at 5 p.m., March 2, 1894. Sparrows in i litre flasks. 4 in series. 



The + mark indicates the death of the animal. 



