98 PROTOZOOLOGY 



Ascorbic acid has been found to be an essential factor for the 

 growth in Leishmania donovani, L. tropica, Trypanosoma cruzi 

 (Lwoff), Tritrichomonas foetus (Cailleau), etc. Haematin is said to be 

 a necessary growth factor for the two species of Leishmania and Try- 

 panosoma cruzi (Lwoff). Observations on the effect of vitamins as ap- 

 plied to host infected by Protozoa are meager. Becker and his associ- 

 ates (1941) have shown that when a ration somewhat restricted in 

 vitamins Bi and Be was used as basal, the addition of moderate 

 amounts of thiamine chloride resulted in a reduction in the number 

 of oocysts of Eimeria nieschulzi eliminated by host rats. The same 

 was true when vitamins Bi and Be were administered to infected rats 

 intraperitoneally in normal salt solution. On the other hand, vitamin 

 Be supplement alone produced an increase in the oocyst production. 



Certain substances which are sometimes called growth stimulants 

 have also been applied to Protozoa in recent years. Elliott (1935) 

 found that pantothenic acid brings about a doubling of the growth 

 of Colpidium campylum in sterile culture at pH 5.5-6.6, but not at 

 pH 7.0 or above, and it does not accelerate the growth of Haemato- 

 coccus pluvialis in bacteria-free cultures. Thus it appears that panto- 

 thenic acid has no effect on chlorophyll-bearers. As to the effect of 

 auxins (plant growth substances), the same investigator demon- 

 strated that Euglena gracilis grew faster in a medium at pH 5.6 in 

 light and in the presence of auxins, while these substances did not 

 bring about any noticeable effect on such colorless forms as Khawk- 

 inea halli and Colpidium striatum. Hall (1939) examined the effect of 

 pimelic acid on Colpidium campylum in sterile cultures and found 

 that it exerts some sort of catalytic effect on the metabolism of this 

 ciliate in peptone and gelatin media, as shown by an increase in the 

 growth rate and in the density of population, but the effect may be 

 masked, or perhaps, eliminated by the addition of dextrose to the 

 medium. 



Fuller information on the relationships between endocrines, vita- 

 mins and growth-promoting substances and Protozoa is dependent 

 upon a greater application of sterile culture method and standard- 

 ization of basal culture media to many Protozoa in future. 



The reserve food matter 



The anabolic activities of Protozoa result in the growth and in- 

 crease in the volume of the organism, and also in the formation and 

 storage of reserve food-substances which are deposited in the cy- 

 toplasm to be utilized later for growth or reproduction. The re- 

 serve food stuff is ordinarily glycogen or glycogen ous substances, 



