No mammal or bird produces substances that are toxic in the practical sense, although all elaborate catabolic substances that are so in about the same relative degree as those of man. While, for the sake of convenience in preparing vehicles, or on account of the value of ferments and nutrients, certain animal products are included in the pharmacopoeia, no animal food stuff is strictly medicinal, in the ordinary sense, and none is toxic in any serious degree, except by reason of essentially accidental circumstances.

Tainted animal foods are dangerous, both on account of living microorganisms and their products. There is a marked prejudice, apparently in most cases, well established by experience, against the use of immature meat, but the reason is not obvious and marked inconsistencies in this regard, exist. Animals and birds that live upon carrion and even carnivorous animals generally, have flesh that is relatively toxic, probably on account of the preponderance of nitrogenous waste.

No domestic fish is poisonous, either as food or by virtue of special secretions, barring accidental impregnation with exogenic poison, tainting and disease. In the West Indies all fish feeding on certain coral banks are poisonous and certain foreign fishes are always toxic, while others are poisonous at the breeding season, as the barbel, pike and barbot, the poison being mainly in the roe. Certain foreign fishes, mainly tropical, also have poison organs more or less analogous to those of serpents, but the flesh is not necessarily poisonous.

So far as known, no mollusc is intrinsically poisonous, either by ingestion or by the possession of special poison organs but accidental impregnation with exogenic poisons or tainting is common.

Many medusae and corals are poisonous but as they are practically never eaten by man, this fact is important only as they serve as food for marine animals of higher rank.

Lizards are not poisonous by ingestion, so far as is known, but certain ones contain poison glands in the skin. However, the only one dangerous to man is the heloderma liorridum and the danger of this has been exaggerated.

No crustacean, such as crabs and lobsters, is intrinsically poisonous but idiosyncrasies resulting in gastro-enteric disturbances and erythema or urticaria, are common. Such animals are also liable to accidental impregnation with poison and, more particularly, to tainting. Of the other arthropods (including insects) the only ones at all liable to be used as food are the king crabs of the class arachnids, which are not poisonous, though other orders of the same class include many poisonous centipedes, spiders and insects.

The most highly toxic substances known are included among serpent venoms but the flesh of serpents is never poisonous intrinsically nor is the venom poisonous when ingested, unless in enormous dose or in the presence of solutions of continuity of the alimentary mucous membrane or of failure of the digestive secretions.

Strange as it may appear, no systematic investigation has as yet been made to determine the possible value of plants in medicinal and nutrient properties, although those empirically in use as foods or medicines or having conspicuous poisonous effects have been pretty thoroughly investigated. It is especially to be regretted that the inorganic constituents and those of organic nature but neither protein, carbohydrate nor fatty, of our common edible plants, have not been thoroughly determined. The same complaint may also be made regarding animal foods.

The following notes, though very incomplete, are summarized from foot notes in the analytic tables of Atwater and Bryant and, to some extent, from other sources:

Lecithin

7 samples of medium fat, fresh ham, average.......... 0.32%

1 sample of fat, fresh ham, average.................. 0.45%,

8 samples of medium fat, fresh pork loin, average...... 0.35%,

8 samples of fresh pork tenderloin................... 0.51%

8 samples of fresh pork shoulder..................... 0.25%

8 samples of fresh pork sides........................ 0.35%:

8 samples of fresh pork clear backs.................. 0.21%

8 samples of fresh pork clear bellies.................. 0.18%

8 samples of fresh pork feet......................... 0.32%

8 samples of fresh pork tails........................ 0.20%

Lecithin is a nitrogenous combination of fatty acids with glycero-phosphoric acid. It is found especially in nervous tissue, yolk of eggs, roe, semen, bile, milk, blood cells and adrenals. It is not known whether it is an excrementitious product or not but it has been advised to prevent the formation and to aid the solution of biliary calculi.

Phosphorus. This substance is a necessary ingredient of bones in the form of calcium phosphate, with a small quantity of magnesium phosphate. Soluble phosphates of sodium and potassium also occur in the blood and body juices generally but it is doubtful whether they are necessary for osmosis or other purposes. Phosphorus is an ingredient of many forms of protein as well as of lecithin, nucleins and higher compounds of purins and is supposed to be especially important in the nervous system. It is probably necessary to the body in complex organic form, in much the same way as nitrogen, but on a smaller scale.

Fish are popularly supposed to be a "brain food" because of their high content of phosphorus but this notion is largely due to the phosphorescence of decaying fish, a phenomenon produced by saprophytes and probably not in any way connected with the presence of phosphorus. However, fish do contain phosphorus in amount corresponding to about 1/2% of the total edible portion, estimated as phosphoric anhydride. The same is true of molluscs and crustaceans. The variations are from 1/5 to 7/10% but not enough analyses are available to determine whether the differences are characteristic of different kinds of sea food. Fish do not, in general, contain more phosphorus than ordinary meat.