The nature of sterilization, and the difficulties in securing it, as well as the extreme delicacy of the manipulations necessary, made it possible for a very long time to be doubtful as to the application of the phrase omne vivum e vivo to the microscopic world, and there still remain a few belated supporters of abiogenesis.
Variations in the bactericidal action of the serum in vivo, variations in the chemiotactic or opsonic properties of the serum in vivo, and variations in the digestive properties of the leucocytes of the particular animal.
From the 17th century onwards it was gradually shown that, at least in the case of all the higher and readily visible organisms, abiogenesis did not occur, but that omne vivum e vivo, every living thing came from a pre-existing living thing.
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