176 
THE ENERGY OF THE LIVING PROTOPLASM. 
oxidation products, as carbohydrates from fats in plants / 11 and it 
helps to prepare from different materials the necessary starting 
groups for protein formation (cf. Chap. V). 
While a unicellular organism obtains the necessary oxygen 
by a simple diffusion process, more or less complicated contri¬ 
vances are necessary to provide the interior cells of multicellular 
organisms with air. Stomata, lenticells, and intercellular spaces 
serve this purpose in the vegetable kingdom ; tracheids, gills, 
lungs, haemoglobin, in the animal kingdom. Movements of the 
abdomen and thorax in insects, of the gills in aquatic animals, 
of the chest in lung-bearing animals, maintain the exchange of 
oxygen against the resulting carbon dioxide. Certain insects, as 
the larvae of the Libcllulidœ , and even a fish (Cobitis fossilis), exhibit 
the remarkable exception, of carrying on their respiration by the 
intestines , which are provided for this purpose with innumerable 
blood vessels. 
Not all organisms, however, produce their physiological 
energy by respiration ; the fermentative organisms gain it with¬ 
out the aid of oxygen, by decomposition of organic matter, 1 (2) 
Bacteria can utilise various hydroxy-acids, proteids, poly¬ 
valent alcohols and sugars, while the yeasts certain kinds of 
sugar only. We have here the case of the so-called intramolecular 
respiration before us, one which yields considerably less energy 
than normal respiration. Also certain animals can for a limited 
(1) The formation of organic acids is also due to respiration, viz., to an imper¬ 
fect oxidation of sugar in most cases. An interesting example is furnished by the 
flowers of Ipomœa triloba , which are blue in the morning and remain so during 
cold foggy, and rainy days, but turn red on warm bright days. Since this change 
from blue to red can also be easily accomplished by acids, we must assume that the 
increased respiration on warm days causes the production of acids. 
(2) The fact that bacteria can be deprived of their fermentative faculties, 
without their life being impaired and thus be turned from anaërobs into obligate 
aërobs, has led me to the view, that there exists a special organoid in those organisms 
endowed with fermentative action. This would, to a certain degree, be analogous 
to the chloroplasts of green plants ; the latter prepares suitable material for growth 
from carbonic acid, while the former prepares it by decomposing various organic 
matters. A small fraction of these fermenting compounds does not appear in form of 
fermentation products, but in that of new cells of the fermenting organism. We see 
therefore, here also a double part played, viz, that of liberating energy and that of 
preparing the necessary groups for protein formation. Cf. O. Locw , Centralbl f. 
Bactériologie 9, Nr. 22. 
