224 Dr. C. Meijmott Tidy [March 2, 



As a general rule, a substance that combines with oxygen with 

 difficulty, parts from it with ease, and vice versa. It is difficult to 

 make gold combine with oxygen, but it is easy to decompose oxide 

 of gold. Potassium easily combines with oxygen, but it required 

 the genius of a Davy, and the resources of the Eoyal Institution, 

 to separate potassium and oxygen. 



In haemoglobin, however, we have a substance that combines 

 with, and delivers up, its oxygen (i. e. is oxidized and reduced) with 

 almost equal facility under similar conditions. Upon this and other 

 chemical characteristics of haemoglobin — as the oxygen-receiver, the 

 oxygen-carrier, the oxygen-deliverer, the carbonic-acid receiver, 

 carrier, and deliverer — the act of living depends. In other words, 

 life depends on the integrity of the haemoglobin — on the rhythmicity 

 of those chemical processes, in effecting which haemoglobin is the 

 primary worker. 



With these facts before us, let us turn to the toxic action of 

 carbonic oxide. 



The haemoglobin at once seizes upon and combines with the 

 carbonic oxide, carbonic-oxide-haemoglobin being formed. 



Two difficulties arise : 



1. The haemoglobin, saturated with carbonic oxide, cannot combine 

 with oxygen. Regarding haemoglobin as a common carrier, the car- 

 riage is full. 



2. The haemoglobin, being saturated with carbonic oxide, cannot 

 get rid of the carbonic oxide under the ordinary conditions of respira- 

 tion and circulation. Again, regarding the haemoglobin as a common 

 carrier, the vehicle, full up, cannot be unloaded. 



To put all this in scientific phraseology, carbonic-oxide-haemo- 

 globin is a comparatively stable compound, being neither decomposed 

 by the presence of an excess of oxygen (as in the lungs) nor by 

 carbonic acid. What must happen ? The man dies because the 

 integrity of the haemoglobin has been disturbed — because the normal 

 sequence of its oxidation and reduction has been interrupted by the 

 formation of carbonic oxide haemoglobin. 



We call the result of all these chemical actions and interferences, 

 poisoning by carbonic oxide. 



3. Strychnine (the poison derived from St. Ignatius' Bean). 

 How does strychnine act ? Wo know sadly little about it — so 



little that we use the phrase " physiological action " to express out 

 want of knowledge. But we know something. 



A marked chemical characteristic of strychnine is its power to com- 

 bine with oxygen when the oxygen is presented to it in a nascent form. 



Note then the conditions. Strychnine is in the body. There is 

 also present in the blood, haemoglobin loosely combined with oxygen, 

 which oxygen the haemoglobin is always ready to give up on first 

 demand. We are able to trace this action, and to see that the period 

 of the primary strychnine fit coincides with the reduction of the 

 hsemoglobin. 



