ANAEROBIC METABOLISM 215 



themselves and not merely by contaminants. Only a few 

 of the most important of these reasons will be mentioned 

 here ; further evidence will be found in the papers of Wein- 

 land (1901) and of von Brand (1934). 



In the first place the experiments summarized above 

 concerning the trypanosomes and Tetrahymena were car- 

 ried out under strictly sterile conditions. They there- 

 fore show conclusively that the production of acids other 

 than lactic acid is quite possible in the case of animal pro- 

 toplasm. Secondly, the presence of fat can be demon- 

 strated within the excretory system of such helminths as 

 Fasciola (Fig. 5) or Moniezia. In so far as the ascarids 

 are concerned, the situation resembles, in principle, that 

 encountered in the above flat worms, though the lower 

 fatty acids cannot be demonstrated within the excretory 

 system of ascarids by staining methods. It has, however, 

 been shown (Weinland, 1902; Schimmelpfennig, 1903; 

 Flury, 1912) that the same fatty acids which are recov- 

 ered from the saline in which the worms were kept can 

 also be isolated from the worm body proper. Weighing 

 the available evidence, the writer considers as quite cer- 

 tain that the helminths are directly responsible for the 

 appearance of fatty acids in their surroundings. How- 

 ever, no final, irrefutable proof is available, no experi- 

 ment having been made in which these acids were isolated 

 while the worms were kept under rigidly sterile condi- 

 tions. With recent improvements in the technique of 

 maintaining helminths aseptically such experiments 

 should be possible in the not too distant future. 



The experiments of Stannard, McCoy and Latchford 

 (1938) with Tnchinella larvae are of particular interest 

 in that they reveal a type of metabolism which differs 

 considerably from that of all other worms. These larvae 

 produce no organic acid whatever, a fact which is of great 

 importance because it shows that lactic acid does not nec- 

 essarily appear, even in small amounts, amongst the ex- 



