Later on, he put this thought in the form of an aphorism: 

 "I expect not to stray from the truth if I change the law — 

 that all that lives comes from the egg — to another law — that 

 all that lives comes from fluid" C* J- 02) . In agreement with 

 Lamarck, Pavlov imagined that fluid appears at the beginning, 

 by whatever means. It then forms into cellular tissue, and 

 from that a living body develops. For life to appear requires 

 an organic interaction between fluid and the cellular tissue. 

 This organic movement occurs through the stretching of the 

 cellular tissue, and the latter responds to the pressure 

 under whose effect displacement of the fluid takes place. 



The fluid contained in the cellular tissue Pavlov, 

 following Lamarck, called the essential moisture (in higher 

 animals, this is the blood; in lower animals, uncolored 

 fluid; according to Pavlov, this latter is ichor) . The first 

 organic movement, according to Pavlov, makes possible the 

 appearance of the basic life function — nutrition, which he 

 considered the application of assimilated particles on dense 

 formations, in which there are always cavities or canals 

 containing the circulating essential moisture. This last 

 disperses continually, and the organism needs its replacement 

 through nutrition. The essential moisture must be variable 

 in different animals, becoming more complex in composition as 

 the animal's organization increases. Thus, in infusoria and 

 polyps, the essential moisture is represented in a fluid 

 watery jelly; in insects it is thicker; in Crustacea, annelids, 

 and molluscs, it has a more complex constitution and contains 

 little protein; in fish and reptiles there is not only protein 

 but also fibrous material in the blood. 



The process of assimilation of food is also related, 

 Pavlov continued, to organization; hence more complex processes 

 of assimilation correspond to complexity of the digestive 

 tract. Likewise with the intake of oxygen, which Pavlov 

 believed participates in the final stage of assimilation, 

 especially in the formatiop of blood, which is not directly 

 contained in the food. The source of development for these 

 substances, Pavlov thought, can hardly be sought in oxygen 

 alone. "Undoubtedly," he said, "such an extremely effective 

 force, which is considered vital, can be called an assimilating 

 force" (5 118). 



170 



