An * after an author's name refers to the reference in the index of names. 



PART IV. 

 CHAPTER XXII. 



TOXICOLOGY AND PHARMACOLOGY. 



IN the following chapter we shall chiefly consider the action of 

 foreign chemical substances and organisms. If only monera (bac- 

 teria, protozoa and yeasts) were involved, the matter would be rela- 

 tively simple; we might regard them as suspensions and approach 

 their investigation with exact physico-chemical methods. It may be 

 seen from the chapter on "Disinfection and Agglutination" that 

 these viewpoints have been successfully employed. 



Some of the substances which are injurious to monera (bacteria, 

 protozoa, etc.) we call disinfectants, and some preservatives. One of 

 the ways by which they are tested is to add the solution under exami- 

 nation to a suspension of bacteria in water or bouillon and observing 

 in what concentration growth is inhibited. It is obvious that this 

 action is dependent upon the concentration and distribution of the 

 disinfectant between bacteria and solvent. Similar experiments may 

 be performed on higher aquatic animals. 



The problem becomes much more complex in the case of multi- 

 cellular organisms, especially the higher terrestrial animals, where 

 the action may be affected by the portal of entry. Water, so essential 

 to life, becomes a poison when injected intravenously. 



Depending on their point of entrance, substances must pass through 

 membranes, filters or places with digestive ferments (stomach, intes- 

 tines, etc.). This may either determine the action and the course 

 taken by the poison or drug, or it may even entirely block its en- 

 trance. Since small intestines and colon send their blood through 

 the portal vein to the liver, substances which are taken by mouth may 

 have no effect in spite of being well absorbed if they are strongly 

 adsorbed by the liver, as happens in the case of potassium salts, 

 curare, etc. Only such substances are absorbed through the skin 

 as are soluble in its fats. 



The action of diphtheria antitoxin when injected intravenously is 

 500 times stronger than when it is injected subcutaneously (W. 

 BERGHAUS). [This has been shown by PARK to be due to its slow 

 absorption from the tissues. Tr.] 



359 



