PROTEIN REGENERATION 21 



to be simple amino acids, polypeptides, etc., in the light of the statement 

 that non-coagulable proteins are sometimes present in the plasma. 

 Bergmann (62), utilizing the method introduced by Fischer and Bergell 

 of shaking the material to be tested with /9-naphthalene sulphochlor- 

 ide and separating out the amino acid compound which is formed 

 states that he was able to obtain from the blood of a patient suffering 

 from acute yellow atrophy a product which crystallized out, but which 

 he could not identify. He also obtained evidence of the presence of 

 bodies which could unite with the /^-naphthalene sulphochloride, but 

 which he was also unable to identify in the blood of dogs killed after 

 an abundant flesh meal. Further in the blood and expressed juice 

 from muscles and liver of an animal which had fasted he was un- 

 able to demonstrate the presence of any material which would com- 

 bine with the /S-naphthalene sulphochloride. Howell (204) used the 

 same method, but, by an ingenious device he got rid of the serum 

 proteins without the risk of losing part of his amino acids in the 

 coagulum formed on heating. He enclosed the blood taken from fed 

 and fasted dogs, in sacs of collodion and dialysed it against distilled 

 water. Amino acids and substances as complex as the proteoses will 

 pass through this membrane. Howell found evidence of amino acids 

 being present in the portal blood of well-fed animals in greater amount 

 than in the systemic blood. Even after fasting for fifty hours he 

 states that a positive amino acid reaction may be obtained from the 

 blood. He also found that the lymph collected from the thoracic duct 

 after a meal gave a positive reaction. Although Howell obtained 

 these positive reactions he did not obtain a pure crystalline body but 

 a sticky substance which he could not identify. This may be and 

 probably is due to the fact that the material present in the blood and 

 which dialyses out is mostly in the form of mixed polypeptides and 

 individual amino acids, none of them in sufficient quantity to enable 

 purification by crystallization to be carried out. 1 



Hohlweg and Mayer (198) have also taken up the question of this 

 " residual nitrogen ". They found a constant increase of this residual 

 nitrogen in the blood of fed dogs above that taken from the fasting 

 animal. In fasting there was present in 100 c.c. serum 0-0525 grm. 

 total residual nitrogen and 0*0384 grm. urea, whereas in the digesting 

 animal there was present in the same amount of serum 0-0788 grm. 

 residual nitrogen and 0-0567 grm. urea. In both cases urea formed 



1 Professor O. Folin has informed me that working in conjunction with Dr. Denis he 

 " has traced in cats both urea and glycocoll from the small intestine into the blood and from 

 the latter into the muscle ". Jan. 1912. 



