PHYSIOLOGY OF THE IXVERTEBRATA, 89 



suspended. The test-tubes are then placed in an incubator* 

 heated to about 40^ C. At the end of an hour or so, 

 the fibrin which is in the alkaline extract has almost en- 

 tirely disappeared ; leaving only a small quantity of finely 

 divided detritus. This liquid contains peptones. 



The neutral extract acts in a similar manner, except that 

 the fibrin is dissolved a little more slowly ; it takes from five 

 to six hours to complete the digestion. This liquid also 

 contains peptones. 



The most concentrated acid extract has no action on the 

 fibrin, which swells, but remains intact during many days. 

 On the other hand, the "fibrin is dissolved more or less 

 completely in the dilute acid extracts, but to do this it 

 requires from thirty-six to forty-eight hours. 



The ferment in which Lnmhricus dissolves the fibrin acts 

 well in a neutral solution, better in an alkaline solution, and 

 badly or not at all in an acid solution ; these properties 

 entirely resemble those of trypsin or the pancreatic ferment. 



The neutral extract converts starch into glucose. The 

 aqueous extract, therefore, contained a substance or ferment 

 which acts in a similar manner to diastase. 



Fredericq having dissected a large earthworm (under 

 water), removed the whole of the alimentary canal, and 

 obtained from the intestine a fluid which is slightly alkaline 

 and readily digests fibrin. This alkaline fluid is secreted by 

 the glandular tissue which almost covers the intestine. The 

 organ has been termed a " liver," whereas it is a true 

 pancreas. The names " bile " and " liver " have been 

 employed at random by a great number of those who have 

 investigated the anatomy of the Invcrtchrata. Nevertheless 

 the princijDal characteristics of the bile (pigments and biliary 

 acids) have never been discovered witli exactitude in any 

 animals lower than the cranial Vertebrates. There is nothing 

 in this fact which ought to surprise us, because it is 



* Like the incubators used in bacteriological laboratories. See 

 Griftiths' lienearc/ies on Micro-Oryunisms, p. 17. 



