METHYLAL.194 Vol

Osakada, K. and Takeuchi, D. Coordination Polymerization of Dienes, Allenes, and Methyl-enecydoalkanes. Vol. 171, pp. 137-194. 

Our knowledge of alkaloids in animals is scant. The so-called protoalkaloids (biogenic amines and their derivatives) are widespread in lower animals (194, 195), and the parallelism between plant and animal metabolism is extensive. Betaines, methylated purines (e.g., paraxan-thine (VI) ), derivatives of histidine (spinacine (VII) of the shark), and kynurenic acid (VIII) are not rare in animals. The animal alkaloids, with the exception of samandarine (Vol. V, p. 321), are characterized as weak bases this is perhaps of importance for their excretion. 

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