PEAS.

§ 99. The pea is, without doubt, the most important of all the leguminous plants. The garden pea is derived from the Pisum sativum, a native of the south of Europe, but long naturalised in this country. The field pea, grown for the purpose of feeding cattle, is the Pisum arvense.

Forty-one analyses collected by König give the following values:

The 53.24 per cent. of non-nitrogenous soluble matter is composed of 36.03 starch, 5.51 dextrine, and 11.70 other substances, among which is some sugar. Cholesterine is also found in peas, but there have been no researches as to its exact quantity. The most important principle of the pea is "legumin." Its amount varies in different species. Thus, H. Ritthausen found in the green field pea, 3.95 per cent.; in the yellow, 9.45, and in the grey, 7.30 per cent.; in the garden pea, 5.40 per cent.

In the young unripe condition, peas contain much more water than the proportions given above. Thus, Grouven found in young unripe peas and beans the following

:

The albumen of peas (which may be obtained by boiling the solution after it has been freed from legumin) differs from ordinary vegetable albumen, both in elementary composition and in its behaviour to reagents. An analysis gives the following percentages

C, 52.94; H, 7·13; N, 17·14; S, 1·04.

After coagulation it dissolves in potash water to a clear liquid, which is not the case with vegetable albumen.

The analysis of the ash of peas gives the following as the extremes and mean of twenty-nine analyses:-

Peas, when putrid, undergo some peculiar change not yet investigated, resulting in the formation of a poison, perhaps similar to the cadaveric poisons described in the second part of this work.*

For the general analysis of peas, the water, the ash, and the amount of starchy matters are estimated by the processes already detailed. To separate the legumin, the peas must be powdered, or, if fresh, mashed into a paste, and treated with successive quantities of cold water, which may be advantageously feebly alkaline, but must not have the least trace of acid. The legumin may now be precipitated by acetic acid, the precipitate dissolved in weak potash, again precipitated, and then dried and weighed.

*Not very long ago a case of wholesale poisoning from this cause occurred in Salford. Many persons who had partaken of slightly decomposed peas exhibited symptoms of irritant poisoning. The peas were chemically examined, but contained neither arsenic, copper, lead, or other metallic poison. [Phar. Journ. (3), 294.] The subject of the formation of new and poisonous substances in such an article of food would well repay investigation. In Germany there has been used a condensed food made up of powdered and dried meat, incorporated with pea-meal, by strong pressure; it is scarcely necessary to say, that in this manner a food invaluable for the soldier is obtained, and one that contains in a very small compass all the essentials of nourishment. An analysis of these pea-meat tablets is as follows:

A condensed pea soup is also prepared. Two analyses of this condensed soup, given by König, are as follows:

Legumin is almost insoluble in cold or warm water; but since it may be extracted so easily from the fresh seeds, it is supposed to be in combination with phosphates of the alkalies when in its natural condition. But it is easily soluble in diluted alkaline liquids, and also readily dissolves in a solution of alkaline phosphates; if boiled it becomes insoluble in alkalies. Pure alkaline solution of legumin shows, with a little cupric sulphate, a beautiful violet colour. If impurities are present, such as gum or starch, the colour is blue. On boiling the alkaline solution, the legumin does not coagulate, but, as in the boiling of milk, a scum of altered legumin appears on the surface.

§ 100. Preserved Peas.-Copper in Peas.--Peas are preserved in several ways, sometimes by simply drying, when they form the wellknown dried peas of the shops. But the more modern method is to heat the peas in a suitable tin capable of being hermetically sealed. The sealing is effected while the tin with its contents is at a high temperature. The rationale of the process is, that putrefying germs existing on the surface of the peas are destroyed, and fresh putrefactive agencies are prevented from gaining access by the exclusion of air. Peas so preserved may, as proved by analysis, be quite as nutritious as fresh peas. Preserved peas have often undergone a preparatory treatment by boiling in copper vessels, the object of which is to impart a fine green colour. M. Guillemare and M. Lecourt have, however, now patented a process by which chlorophyll has been substituted for the objectionable coppering. The copper that has hitherto been found in tinned peas has amounted to about 2 grains to 2.6 grains in the pound tin, and the question arises whether the copper is injurious to health in this proportion or not. In the cases appended to this article it will be noticed that men of considerable scientific reputation have expressed strong opinions on the subject; nevertheless, the whole of the injurious action of coppered peas rests entirely on theory, and in no single instance (although the consumption of coppered peas has been very large) has any really definite case been brought forward of actual poisoning by peas coloured in this way. It is perfectly true that it is not necessary for symptoms to arise, in order to pronounce whether a particular substance would be likely to be injurious or not; for example, the question would be answered readily enough that cyanide of potash was poisonous if in a certain quantity, although people might have taken small doses of cyanide of potash for some time without any apparent injury. But here the case is different; for it is by no means certain in what particular combination the copper exists, for if the copper should exist in a state of combination with some organic matter-for example, the legumin, so as to be insoluble

in the digestive juices, although the fact of such insoluble compound would render the peas less nutritious, yet they would have no toxic action. Legrif has found in the intestine of a healthy man 036 to 040 grm. of copper ;* and Messrs. Paul and Kingzett have shown that, even when a soluble compound, like sulphate of copper, is ingested, most of it is excreted by the fæces.

The author, therefore, concludes that it would be best, in our present state of knowledge, to decline to state whether copper, when it exists in the moderate proportions given above,t would be likely to injure health, since there are no definite facts upon which to base a sufficient opinion. On the other hand, since coppered peas must either, (1.) have a toxic action, if the copper is in a soluble form, or, (2.) if the copper is insoluble, the pea must be deprived of some of its nutritious properties, the analyst need have no hesitation in certifying that peas made green with adulterated under the Sale of Food and Drugs Act.

copper are

The method of detecting copper in peas is as follows:-A weighed quantity of the peas is made into a paste with water and a little hydric chloride, and the paste is placed in a proper platinum dish; a rod of zinc, on being inserted in the paste, so as to touch the platinum dish, sets up a galvanic current, and at the end of several hours all the copper is deposited as a coherent film, and may be dried and weighed. A neater process is the connection of the platinum dish with the negative pole of a battery, while the positive pole is suspended in the acid paste. In both instances the copper is deposited as copper.

Tinned peas may contain traces of tin. The process for the detection of tin is as follows:-A sufficient quantity of the peas is incinerated in a platinum dish, the ash is heated with strong hydric chloride, and evaporated nearly to dryness; a little water is then added, boiled, and the solution filtered. This method of extraction is repeated once or twice. The solution is now saturated with hydric sulphide, and any yellow precipitate filtered off. This should present the characters of sulphide of tin. Tin has been found, according to Mr. Hehner, generally in tinned goods to the amount of 10 mgrms. in the English pound, and it has been supposed, without adequate proof, to exist as a stannous hydrate, a tin compound which is poisonous.

No prosecution has hitherto taken place with regard to tin in preserved goods; and in such small quantities as have hitherto been found, it is very questionable-presuming the tin to exist as stannous hydrate-whether any injury would result.

A few of the more important prosecutions for coppered peas may, in conclusion, be quoted:

* Sonnenschein. + Analyst, 1877, p. 98. + Analyst, 1880, 218.

In one of several similar cases heard at the Marlborough Street Police Court, it was proved by Mr. Piesse, the analyst, that the pound tin contained 088 of copper, equal to 24 grains of sulphate of copper.

Dr. Conway Evans, Medical Officer of Health, stated his opinion, that the larger quantity of copper spoken of in a pound of peas, if eaten daily or repeatedly, would be injurious to health, and would produce chronic poisoning; but many persons might eat a quantity of these peas several times without apparently suffering any injurious effects, the period varying in accordance with difference of vigour, age, health, &c. Two or three doses might affect some persons and not others. From 14 to 15 grains of copper were sometimes given as an emetic; and sometimes, in ague or chronic diarrhoea, to 3 grains were given as a tonic. It was a well-known medical fact, that in regard to some poisons (such, for instance, as mercury) certain persons were peculiarly susceptible to their influence; and it was possible that these peas containing copper, if swallowed by persons ignorant of their own susceptibilities, might (even in a single dose, or a few doses) lead to injurious consequences. He believed copper to be more fatal, in a smaller dose, than salts of lead. The heightening of the colours of preserves with copper was once a common practice. Cases of poisoning by copper were formerly very common, but copper utensils in cooking having given place to tin and iron saucepans, such cases were of rare occurrence. Pure metallic copper he believed to be harmless, but it was dangerous when in contact with other substances, and when dissolved.

Dr. Guy, F.R.S., said that cases of poisoning by copper had occurred in which the quantity swallowed must have been small. He had studied the question of poisons particularly; the fact of a trace of copper in the human body would not prove its existence in a poisonous form. He had made inquiries for Government into the effects of poisoning in certain trades; palsy followed the poisoning by copper. Two cases had come under his knowledge of poisoning by the green wall-paper in a room; the poisoning in his opinion came from the copper, not the arsenic. Salts of copper be considered more poisonous than lead; the small quantity of copper contained in the peas in question from France might prove injurious, and slowly undermine health. On a nervous person copper was more likely to produce dangerous symptoms than on any one else. With regard to the presence of 36 of copper, if taken one-third at a time, it would not affect a healthy person; but if repeated in small doses it would, in his opinion, be ultimately injurious to health. He considered that any article containing the amount of copper stated by Mr. Piesse should not be allowed to be sold for one moment. Sulphate of copper in its virulence ranked fourth in the class of poisons.

Dr. C. Tidy gave similar evidence. If copper, that is, sulphate of copper, were constantly taken to the extent of the amount of copper found in the French peas, it would be injurious to health.

Dr. A. Dupré stated that the quantity found was far beyond the quantity normally present in any vegetable.

Dr. Guy said he considered the sale of an article containing such a quantity of copper as that found in the French peas ought not to be tolerated. Small doses of copper were more dangerous than large ones, as the latter would cause vomiting.

A previous conviction against the defendant for the same offence was proved, but the prosecution stated that they desired publicity, not punishment, and a small fine was inflicted.*

Analyst, 1877.