NUTRITION 125 



cytoplasm, as various ferments have been extracted from Protozoa. 

 Generally speaking, the reaction of a food vacuole is at first acid when the 

 ingested organism is killed. The reaction then becomes alkaline. It is 

 probable that during the acid phase a peptic ferment is active, while a 

 tryptic ferment is present during the alkaline phase. Fats also are 

 capable of being digested. It sometimes happens that the contents of 

 a food vacuole are alkaline from the commencement, and it appears that 

 the cytoplasm has some power of varying its response to different types 

 of food. 



The proteid material absorbed from the food vacuoles, or from the 

 medium in which the organism is living, enters the cytoplasm, and is 

 immediately elaborated into the constituents of the cell or leads to the 

 formation of various intermediate bodies. The latter may be regarded as 

 food-reserve materials which are merely accumulations resulting from the 

 intake of excess of nourishment, or definite reserves intended for a period 

 of excessive activity, such as occurs during the sporogony process of 

 coccidia and gregarines, or the continued development when access to 

 nourishment is prevented, as when a cyst wall is present. 



In the organisms which have a holophytic method of nutrition the 

 food reserve is stored largely as starch or allied substances of an amyloid 

 nature. In gregarines preparing for sporogony in the gametocysts the 

 cytoplasm becomes charged with refractile globules of a substance called 

 paraglycogen. The macrogaraetocytes of coccidia, which are to continue 

 development in an oocyst, likewise become loaded with refractile globules 

 of an albuminous substance. Similarly in the encysted stages of Entaynoeha 

 histolytica, lodamoeha biltscMii, and other forms, a large amount of a 

 glycogenic substance is present. It is gradually used up during the period 

 passed by the encysted form in awaiting a suitable opportunity for emerging 

 from the cyst. Another substance which is often present is volutin, which 

 appears in the fresh condition as greenish refractile globules. It stains 

 deeply with many nuclear stains, and has been supposed to be a forerunner 

 of chromatin, but of this there is no direct evidence. Many of the granules 

 which have been described as chromidia are probably of this nature. It 

 commonly occurs in flagellates, and is often abundant in trypanosomes, 

 appearing as deep red granules in specimens stained with Romanowsky 

 stains. Fat globules also occur in Protozoa, and are commonly present 

 in Radiolaria. The identification of the various granules and reserve 

 substances is a very difficult matter, dependent on microchemical tests, 

 solubility in various fluids, and reaction to different stains. 



The residue from food digestion, as pointed out above, is discharged 

 from the body. This may occur immediately after digestion is completed, 

 or it may be deferred. The substances may assume different forms. 



