PHYSIOLOGY OF THE INVERTEBRATA. 93 



The presence of glucose was proved by the formation of red 

 cuprous oxide by the action of Fehling's solution. 



Another portion of the secretion was distilled in a minia- 

 ture retort (made of glass tubing) with dilute sulphuric acid. 

 To the distillate ferric chloride was added, which produced a 

 red colour, indicating the presence of sulphocyanates. 



The secretion of these glands yields a small quantity of 

 ash, which contains calcium phosphate. 



The soluble ferment of this secretion may be isolated by 

 precipitating an infusion of the glands obtained from a large 

 number of these insects with dilute phosphoric acid, adding 

 lime-water, and filtering. The precipitate is then dissolved 

 in distilled water, and re-precipitated by alcohol. This 

 precipitate converts starch into glucose, but has no action 

 on fibrin ; in other words, it has a similar action to ptyalin 

 — the ferment of the saliva of the higher animals. It is 

 probable that in Blatta there are terminations of the nerves 

 in these salivary glands. It may be that these nerve- 

 endings affect the protoplasmic substance of the cells forming 

 the ferment, which has the property of converting starch into 

 glucose. 



The crop of Blatta simply acts as a receptacle to store up 

 the rapidly swallowed food until time is afforded for the food 

 to be passed on to the true stomach. 



The gizzard or proventriculus has been described in the 

 last chapter. It is considered by some to be an internal 

 masticatory apparatus, but M. Plateau,* considers that the 

 proventriculus of Blatta acts simply as a strainer. 



The chylific ventriculus may be termed the true stomach 

 of Blatta, for it is probable that digestion is more active in 

 this than in any other part of the alimentary canal. It is 

 lined with epithelium, and often contains peptones. 



The pyloric caeca, situated in front of the chylific ventri- 



* See his papers on the digestion in the Myriapoda, Inseota, and 

 Arachnida, published in the BuMetin de I'AcadSmie Moyale des Sc'ences de 

 Be'gique, 1874-78. 



