the secondary aerobic process is present. Harnisch (1937) of- 

 fered support of this view in the observation that washed 

 minced Ascaris material has only a negligible oxygen consump- 

 tion. The same material, suspended in Ascaris body fluid, has 

 a very high oxygen consumption and surpasses even that of 

 non-minced material. According to Harnisch this indicates the 

 presence of a powerful oxidizing mechanism outside of the cells 

 which may govern the entire aerobic processes of Ascaris. 

 This, he claims, is in accordance with his explanation of ex- 

 periments with artificially induced secondary aerobic processes 

 in Chlronomiis. The cellular agents which govern the primary 

 aerobic processes in Chironomns, however, could not be re- 

 moved from the cells by washing (Harnisch, 1936). 



The data of Kempner (1937) show that in a variety of bio- 

 logical materials the effect of oxygen tension on oxygen con- 

 sumption varies with pH, CO2 tension, salt content, and tem- 

 perature. It is apparent that certain tissues heretofore con- 

 sidered to have a respiratory mechanism unaffected by oxygen 

 tension reallj' show an independence only in alkaline COa-free 

 media in a certain temperature range. These observations of 

 Kempner indicate that the whole question of oxygen tension 

 versus oxygen consumption should be reexamined, and that the 

 respiration of no material can be said to be completely de- 

 pendent or independent of O2 tension unless the effects of the 

 above factors have been investigated. It is possible that these 

 factors may have some effect on the nematode data discussed 

 above. A discussion of the theoretical relationship between 

 oxygen tension and oxvgen consumption is given by Marsh 

 (1935). 



It seems that all the different organs of Ascaris are able 

 to consume oxygen. This has been shown for the body wall, 

 intestine, ovaries, uterus and even the body fluid (Harnisch, 

 1935, 1937; Kriiger, 1936). The largest absolute amount is 

 consumed by the body wall, although the intestine shows the 

 highest rate of oxygen consumption. 



It is now generally believed that ascarids evolve larger 

 amounts of carbon dioxide under aerobic than under anaerobic 

 conditions (Weinland, 1901; v. Brand, in34a; Kriiger, 1936), 

 and Harnisch (1937) has abandoned his previous contention to 

 the contrary. The respiratory quotient in air is consistently 

 very high. In fresh worms it may be about 4 or even higher, 

 and in worms kept for several days in saline it is between 1.27 

 and 1.88 (Kruger, 1937). This indicates that the oxidation of 

 metabolites is not complete and that even in the presence of 

 oxygen the metabolism consists in part of anaerobic fermenta- 

 tions. 



The excretion of organic acids under aerobic conditions, fiist 

 seen by Weinland (1901), is definite proof of the presence of 

 fermentations. The acids have been identified as small amounts 

 of lactic acid (v. Brand, 1934a), formic, acetic, and probably 

 butyric acid, a large amount of valeric acid and some unidenti- 

 fied higher acids (Oesterlin, 1937). Since these products are 

 similar to those formed under anaerobic conditions (see above), 

 it seems likely that the fermentations going on under aerobic 

 and anaerobic conditions are identical. The amounts of acids 

 excreted at the oxygen tension of air are definitely lower than 

 under strictly anaerobic conditions (v. Brand, 1934a; Kruger, 

 1936, 1937), but at low oxygen tensions even more acids are 

 excreted (Kruger. 1936). 



It is customary in the nematode literature to refer to the 

 oxidations which involve oxygen consumption and which lead 

 to the production of carbon dioxide and water as oxidative 

 metabolism and to refer to the molecular rearrangements and 

 oxido-reductions which lead to the production of carbonic, 

 lactic, valeric, and other acids and in which oxygen is not con- 

 sumed as fermentative metabolism. Von Brand (1934a) and 

 Kruger (1937), by basing calculations on the ratio of anaero- 

 bically evolved carbon dioxide to anaerobically excreted acids 

 or similar data at low oxygen tensions, calculated the amounts 

 of aerobically evolved carbon dioxide which originated in fer- 

 mentative and in oxidative metabolism. This latter figure was 

 used, in connection with the oxygen consumption, to calculate 

 the true respiratory quotient which was found to be about 0.9 

 or 1.0. In some cases very low quotients were found, and these 

 data are difficult to explain at the present time. The opinion 

 of Harnisch (1933) that the aerobic processes do not lead to 

 the production of CO2 and that the respiratory quotient is 

 zero has been generally abandoned. 



Kruger (1936) found that the uncorrected respiratory quo- 

 tient of ascarids kept in air instead of saline fell rapidly to 

 about 1.0 and remained at this level for some time. This would 

 indicate (Kriiger, 1937) either that the fermentations cease 

 altogether, or that the fermentations present do not lead to 

 carbon dioxide production (e.g., lactic acid formation). 



The question of what substances are oxidized has received 

 some attention by v. Brand (1934a). He found that under 

 aerobic conditions somewhat less glycogen is consumed than 



under anaerobic ones. On an assumption similar to that made 

 above for the carbon dioxide, he calculated the amounts of the 

 consumed glycogen which had apparently been decomposed by 

 fermentative and by oxidative metabolism. He arrived at the 

 following balances: 



Uncorrected balance for 100 gm worms starving at 37° C. 

 under aerobic conditions: 



Decomposed: 1.18 gm glycogen. Consumed: 0.21 gm oxy- 

 gen. End products: 0.84 gm carbon dioxide + 0.10 gm 

 valeric acid + 0.01 gm lactic acid. 

 Oxidative part of the metabolism: 



Decomposed: 0.37 gm glycogen. Consumed: 0.21 gm oxy- 

 gen. End products: 0.34 gm carbon dioxide + ?. 

 Fermentative part of the metabolism: 



Decomposed: 0.86 gm glycogen. End products: 0.48 gm 

 carbon dioxide + 0.16 gm valeric acid + 0.01 gm lactic 

 acid. 

 The amount of glycogen which disappeared was so great that 

 complete oxidation to carbon dioxide and water could not be 

 assumed for all of that which was calculated to undergo oxida- 

 tive metabolism. Probably only a partial oxidation takes place 

 (formation of aldehydes?). 



Harnisch (1935) thought that possibly isovaleric acid would 

 be oxidized to aceto acetic acid or ^Q hydroxy-butyric acid which 

 in turn would lie decomposed to acetone and carbon dioxide. 

 However, chemical determinations on the excreta do not favor 

 this view. This statement applies also to v. Brand's (1934a, b) 

 original theory that fats may be changed into carbohydrate. 



It seems as if Ascaris, in contrast to many free living ani- 

 mals, does not contract a noticeable oxygen debt during a pe- 

 riod of anaerobiosis (Adam, 1932; Harnisch, 1933). It was 

 found (v. Brand, 1937b), however, that ascarids sub.iected to 

 20 hours anaerobiosis and then brought for 2 to 6 hours into 

 aerobic conditions, resynthesized 1/20 to 1/10 of th" glycogen 

 consumed during the anaerobic period. This resynthesis is clear- 

 ly an aerobic process, and it is apparently much l"ss pronou"""d 

 in Ascaris than in similarly treated vertebrate muscles. This 

 may be due to the fact that in vertebrate muscle the end nrnd- 

 ucts accumulate, whereas in Ascaris they are excreted, and only 

 those present in the liody at the beginning of the aerobic period 

 are available for resynthesis. It is unknown whether lactic acid 

 or the lower fatty acids are resynthesized to glycogen. 



There is still some controversy concerning the .significance of 

 the aerobic processes of Ascaris. Harnisch (1933) assumed that 

 the aerobic processes would yield no energy, and he still thinks 

 (Harnisch, 1935) that thev play no role in the normal energy 

 supply of the organism. This view is similar to that of Kriiger 

 (1937) who states that they are probably not linked to any 

 specific organ function and that any derived energy is prob- 

 ably wa.sted. The present writers are of the opinion that at 

 Hiis time no definite statements regarding the possible utiliza- 

 tion of this energy can be made. 



The fact that the rate of the fermentative processes is re- 

 duced at the oxygen pres.sure of air, seems to indicate rather 

 clearly that fermentations and oxidations are not entirely inde- 

 pendent as Harnisch (1933) originally assumed. Whether Krii- 

 ger 's (1937) view is correct that the oxidations follow essen- 

 tially the same course as in truly aerobic organisms, or whether 

 Harnisch (1937) is right in assuming that they correspond only 

 to the secondary aerobic processes occurring in free living ani- 

 mals only under sjiecial conditions, must be decided by future 

 investigations. 



The aerobic metabolism of Parascaris eqvoriim has been 

 studied by Toryn (1934 to 1936b). He found an almost identi 

 cal glycogen consumption under aerobic and anaerobic condi- 

 tions, but since the worms excreted slightly less organic acids 

 under aerobic conditions, he concluded that a small amount of 

 glycogen was oxidized. Apparently the aerobic metabolism 

 of Parascaris follows the same pattern as that of Ascaris. 



The question of whether or not parasitic nematodes use fat nn 

 der aerobic conditions is difficult to answer satisfactorily at the 

 present time. In v. Brand (1934a) aerobic experiments no fat 

 was used. In view, however, that his experiments lasted only 24 

 hours and that in general carbohydrate is consumed before the 

 fat reserves are attacked, these experiments can not be accepted 

 as conclusive evidence that no fat may be used during longer 

 periods of starvation. JIneller (1928/29) observed that in ex- 

 planted pieces of Ascaris a loss of morphologically demonstrable 

 fat occurred after several days, and Hirsch and Bretschneider 

 (1937) have shown that in starving ascarids much of the stain 

 able fat disappeared from the intestinal cells after 6 days. 

 These observations are suggestive that fat may be used, but 

 they should be confirmed by quantitative chemical methods.^ 

 Bondony (1910) detected a lipase in Strongijlus eqitintis, and 

 the possible significance of its presence warrants further study. 



iln a recent paper v. Brand (1914) showed that Ascnrin uses no fat 

 for production of energy during an aerobic starvation period of 5 day». 



364 



