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 w^ords, 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- 



i endings affect the protoplasmic substance of the cells forming 



I 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 

 I to be passed on to the true stomach. 



The gizzard or proveutriculus has been described in the 

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

 masticatory apparatus, but M. Plateau* considers that the 

 proveutriculus 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 ca3ca, situated in front of the chylific ventri- 



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

 Arachnida, published in the Bulletin de, I'Acaddiaie Itojale des /:'ciences de 

 . Be'gique, 1874-78. 



