984 PROTOZOA AND OTHER ANIMALS 



now ed., 1927-1929) he expressed the same opinion, and stated that the 

 physiological role of these ciliates is evidently similar to that of termite 

 flagellates, admitting, however, that they are not so important to the 

 life of the host as these, because ruminants have other aids in cellulose 

 decomposition. Usuelli (1930b) remarked that the softer green plant 

 parts, which are those chiefly ingested, contain relatively little cellulose; 

 so that even if intracellular digestion of this did take place, it would have 

 little quantitative significance in the decomposition of cellulose in the 

 rumen. 



Mangold (1929, 1933) and his coworkers have emphasized the role 

 of the ciliates in protein economy, reasoning that their bodies contain 

 a significant part of the nitrogen available to the host, and that they 

 derive this from plant protein, and presupposing that the ruminants 

 can make better use of this animal protein than they can directly of plant 

 protein. The last fact is certainly fundamental to their thesis, but Becker 

 (1932) remarked that there is no proof of it. Becker, Schulz, and 

 Emmerson (1930) found that goats digested slightly more protein 

 when the ciliate population was present; but the difference was so small 

 as to have little significance without further studies. 



According to analyses by C. Schwarz (1925) of the rumen contents 

 of slaughterhouse cattle, 20 percent of the nitrogen is in the ciliates 

 and 11.7 percent in bacteria. Ferber (1928) found the ciliate nitrogen 

 in sheep and goats, with a population of from 837 to 2079 ciliates 

 per cubic millimeter, to be from 10.27 to 20.33 percent of the total, 

 averaging about 15 percent. Ferber and Winogradowa-Fedorowa (1929) 

 calculated that with a population of 900,000 ciliates per gram and with 

 the total nitrogen 0.166 percent, there would be, in a 3-kilogram 

 rumen content, 150 grams of ciliates. These would contain about 4.7 

 grams of protein, and the estimate would be nearly doubled by use of the 

 figures of Mangold and Schmitt-Krahmer (1927) for the total nitrogen. 

 There is ciliate protein also in the reticulum, but this amounts to only 

 a fraction of that in the rumen. 



There are no exact estimates of the amount of ciliate protoplasm di- 

 gested in a day. Ferber and Winogradowa-Fedorowa (1929), on the 

 basis of a fallacious estimate of a 7-percent daily division (see p. 973), 

 calculated that 2 percent of a sheep's daily protein requirement of thirty 

 grams might be met by the ciliates. In this estimate the higher figures 



