Aleksandr Ugolev’s Raw Frog Digestion Experiment - Original Sources
1984 Soviet Journal Publication (Original Study)
Aleksandr M. Ugolev first published the raw vs. cooked frog digestion experiment in 1984 in a Russian physiology journal. In a paper co-authored with V. A. Tsvetkova, Ugolev detailed the “induced autolysis” phenomenon as a mechanism of digestion. This article (in Fiziologicheskii Zhurnal SSSR im. I. M. Sechenova, Nov 1984, 70(11):1542-50) reports that a raw frog was digested completely in gastric acid, whereas a boiled frog was only superficially affected. The authors found that native (raw) tissues broke down more effectively and completely than the same tissues after heat denaturation, demonstrating that food’s own enzymes contribute significantly to its digestion. (The publication is in Russian, but an English abstract is available.)
Citation: A. M. Ugolev & V. A. Tsvetkova (1984). “Induced autolysis as an important mechanism of the initial stages of ordinary digestion.” Fiziol. Zh. SSSR im. I. M. Sechenova, 70(11): 1542-1550. (Article in Russian; outlines the frog experiment and the concept of self-digestion in raw tissues.)
Accounts in Ugolev’s Books and Later Works
Ugolev later described this experiment in his monographs on nutrition and digestion. In Theory of Adequate Nutrition and Trophology (a book first published in 1987, with later editions in 1991), he recounts a model experiment nicknamed the “little artificial boa constrictor.” In this setup, a “raw” frog and a briefly boiled frog were placed in a chamber of gastric juice (from a carnivore). Initially, the cooked frog’s connective tissues began to break down faster (matching conventional expectations). However, over the next 2-3 days the raw frog completely dissolved (self-digested), while the boiled frog’s structures remained largely intact. This demonstrated that the raw frog’s own enzymes (released from its cells by the acid) helped digest it - evidence of food autolysis at work. Ugolev emphasized that native proteins are hydrolyzed faster than denatured proteins in this context.
This frog experiment and the concept of induced autolysis are also discussed in Ugolev’s earlier book Evolution of Digestion and the Principles of Evolution of Functions (Leningrad, 1985). Together, these works formed the basis of Ugolev’s theory of adequate nutrition, highlighting that living (raw) food carries its own enzymes to aid digestion. The 1987 monograph (in Russian) is a comprehensive source, detailing the frog experiment and its implications for human nutrition and digestive physiology. (No free full-text English translation of the book is available, but the Russian texts are accessible in libraries and online archives.)
References:
- A. M. Ugolev, Theory of Adequate Nutrition and Trophology (Теория адекватного питания и трофология), Nauka, 1987 (in Russian) - see Chapter 1.3.6 for the frog experiment.
- A. M. Ugolev, Evolution of Digestion and Principles of Evolution of Functions (Эволюция пищеварения и принципы эволюции функций), Nauka, 1985 (in Russian) - discusses the concept of induced autolysis in digestion.
Additional Notes (English-Language Context)
While Ugolev’s original publications were in Russian, the core findings have been noted in English-language summaries and later research. For instance, the PubMed abstract of Ugolev’s 1984 paper (above) confirms that gastric secretions plus the food’s own enzymes together cause thorough digestion of raw tissues. This experiment is often cited in nutrition literature as evidence that raw foods can “digest themselves” to an extent via lysosomal enzymes (a process Ugolev termed autolysis).
The primary source for the “raw frog digestion” study is Ugolev’s 1984 journal article. For a more detailed account (in Russian), Ugolev’s books from 1985 and 1987 present the experiment and its theoretical significance.
https://pubmed.ncbi.nlm.nih.gov/6519288/
https://freelibrary.ru/bookread/287574-aleksandr-ugolev-teoriya-adekvatnogo-pitaniya-i/page-5