412 SCIENCE PROGRESS 



starch and cellulose and that malnutrition resulted if they were 

 fed on these substances. 



Much interest has also centred round the work of Sloan 

 (191 5), who, following up Abderhalden's investigations, showed 

 that there was increased proteolytic action of the blood serum 

 during pregnancy. This increase he ascribed in the main to an 

 increase in the polyvalent ferments. The practical importance 

 of this was urged by McCord (191 3), who advocates the sero- 

 diagnosis of pregnancy. It is assumed that the increase in 

 proteolytic power of the blood of the pregnant animal is a 

 protracted process against infiltration by chorionic villi. 



It would be well perhaps to note that the specificity of the 

 " Abderhalden reaction " has many strong opponents. Bron- 

 fenbrenner (191 5), reviewing all the work on the subject, came 

 to the conclusion that no new enzymes were formed, but that 

 the anti-ferments of the normal blood were inhibited ; while 

 Opler (19 16) considers that the apparent specificity is really 

 due to errors in technique, and makes various suggestions as to 

 where these may occur. He considers the position claimed by 

 Abderhalden to be absolutely untenable. One might also 

 mention the work of the latter observer in 19 14. He found that 

 by subjecting a mixture of amino-acids obtained from a 

 definite organ to the action of a maceration juice of the same 

 organ for several months, a decrease in the amount of amino- 

 nitrogen and an increase of coagulable protein occurred. This 

 he attributed to the specific action of the cellular enzymes of 

 the tissue. 



A somewhat similar specificity has been shown in the plant 

 world by Fischer (1919). He found that in the legumins, 

 especially those used for crops, there is a steadily increasing 

 amount of proteoclastic and peptoclastic enzymes, which reaches 

 a maximum at harvest-time. He has also shown that there 

 is a distinct increase in these enzymes at the time of the 

 germination of the seed. 



A degree of specificity is also seen in the influence of certain 

 substances in increasing the output of catalase from the liver, 

 whereby general oxidation is facilitated. This will be dealt 

 with under the. heading of " Oxidation." 



The enzymes of bacteria grown artificially appear to have 

 a direct relation to the medium on which the bacteria are 

 grown. Thus Diehl (191 9) showed that in the absence of 

 organic nitrogen bacteria develop no proteolytic enzymes. 

 When organic nitrogen is added, the enzymes developed cor- 

 respond to the amino-acids added to the culture medium and 

 will attack these whether free or combined in the protein 

 molecule. 



Although the general opinion of investigators tends to 



