The albumens and peptones of the dung are pretty well decomposed and absorbed before evacuation; the bacteria subsequently split up the amido acids into fatty acids and ammonia. The fatty acids are then decomposed generally in the form of the calcium salts, in the manner shown in the table (p. 108), for which I am indebted to Dr. E. Herfeldt, of Bonn. We have already treated of the action of these various products in Chapter II., but it will be seen from what has been said in the present chapter that the chemistry and bacteriology of the puer overlap, and that it is difficult, if not impossible, to separate them entirely. The bacteria are continually manufacturing chemical compounds, and decomposing others. In this respect it is interesting and instructive to note that Nencki, in his classical work “The Chemical Mechanism of Putrefaction,”[85] considers the processes by which the putrefaction of proteids is brought about by bacteria, to be analogous to those taking place by melting the bodies with potash, and he holds the view that in the hydration processes brought about by bacteria, the water plays the same part as the potash. [85] Journ. f. Prakt. Chem., Bd. xvii., 1878; see also Stoklasa, Cent. Bl. f. Bakt. vi., p. 526. ---+-------------+--------------+---------------------+---------------- No.| Fermenting | Cause of | Fermentation | Authors. | Substance. |Fermentation. | Product. | ---+-------------+--------------+---------------------+---------------- 1 |Calcium |Bacteria from |_Calcium carbonate, |Hoppe-Seyler, |formate |sewer slime. |CO_{2} and H_ |Archiv f. d. g. | | | |Physiol. xii. | | | | 2 |Calcium | " " |_Calcium carbonate, | " " |acetate | |CO_{2} and CH_(4)_ | | | | | 3 |Calcium |Thin bacillus |1. _Propionic acid_, |Fitz, nine |lactate | |and, as by-products, |papers in |Undergoes | |_acetic acid_, |the “Berichte |four | |_succinic acid_ and |der Deutsch. |different | |_alcohol_. |Chem. |fermentations| | |Gesellschaft,” | |Other species |2. _Propionic acid_ |1876–1884. | |of bacteria: |and _valerianic | | |short aerobic,|acid_. | | |butyric | | | |bacteria |3. _Butyric acid_ and| | |(Fitz). |_propionic acid_. | | | | | | | |4. _Butyric acid_, | | | |according to Pasteur | | | |(Comptes rend. 1861) |