Biochemical and Biophysical Phenomena 773 



Antibodies are specific chemical substances produced by animal tis- 

 sues when stimulated by specific proteins. For example^ diphtheria anti- 

 toxins are produced by a horse when injected with diphtheria toxin. 

 These diphtheria antitoxins when introduced into a patient act only on 

 diphtheria toxins and not on any other type of toxin, even though it 

 may be present. Antibodies may be formed in several places but espe- 

 cially in the bone marrow, lymph glands, and spleen. Antibodies do not 

 act directly on bacterial cells. Certain white blood corpuscles, known 

 as phagocytes (Gr. phagein, to eat), actually ingest bacteria and destroy 

 them. This occurs when a sufficient amount of a substance known as 

 an opsonin is present (Gr. opsonin, to prepare for). The chemical com- 

 position of opsonins is unknown. Various antibodies are also considered 

 in the chapter on Biology of Man. 



The phenomenon of hypersensitiveness (increased sensitiveness) is 

 probably quite common in living organisms. Most, if not all, of these 

 phenomena are hypersensitiveness on the part of animal protoplasms to 

 protein materials. Their chemical compositions are not exactly known. 

 The susceptibility of an individual to a certain protein material depends 

 on the permeability of the cell membranes of his body to these protein 

 materials. One person may have a type of cell membrane which pre- 

 vents the entrance of a particular protein substance, while another indi- 

 vidual may have cell membranes which permit their entrance. The 

 former would be immune from attacks by that type of substance but 

 might readily be attacked by a different protein material. It is well 

 known that certain foreign proteins when taken into the body in certain 

 states may create a characteristic reaction. These protein materials 

 may be simple proteins which occur naturally, such as plant pollens, or 

 they may be simple proteins which have been produced by the incom- 

 plete digestion of more complex proteins. Our reactions to eggs, milk, 

 strawberries, and similar foods may be of the latter class. Several terms 

 have been applied to such phenomena. Anaphylaxis is applied to acute 

 conditions of hypersensitivity. Allergy (Fig. 256) is applied to the less 

 fatal hypersensitive reactions in man. 



QUESTIONS AND TOPICS 



1. Discuss the specific interrelationships of biology, chemistry, and physics, in- 

 cluding several examples in detail. 



2. Define each of the terms Hsted in this chapter. 



3. State the law of the conservation of energy. 



4. Explain the roles of electrolytes in living protoplasm. 



5. Discuss the permeability of membranes and osmotic pressure as they pertain 

 in living protoplasm. 



