connected with vital phenomena. The animal body is something more than a mere mechanical machine, a mere steamengine, or a mere chemical laboratory; the changes which take place in it subserve more important purposes, the development and manifestation of more recondite phenomena, which deserve and require much investigation for their elucidation.

Before concluding the present paper, I shall just refer to the action of electricity upon the nerves in exciting muscular contraction.

It is well known that contractions arise from the development of the nerve-current in the nerve of the limb,—that is to say, that when the extremity of the nerve is bent over so as to touch the side of the nerve, contractions are produced in the muscles supplied by that nerve. This experiment was known in Galvani's time. Contractions are also produced when the circuit is broken. To obtain these effects, the limb must be fresh and the frog easily excited. It is needless to add, that contractions may be produced by mechanical means, such as irritating the nerve with a needle or a bit of glass; also by chemical means, such as moistening the nerve with a solution of caustic potash, or of common salt, or with strong acids so that electricity itself is not essential for the production of muscular contraction, but it would appear that a change of state in the nerve is the essential condition. Although electricity is not necessary for the production of this change of state (I am not supposing that the electric state of the nerve is not affected), it nevertheless bears a very important relation to nerve force in the production of this change of state, as is manifested in the difference of effects observed in regard to the direction of the electric current when made to traverse a nerve. Let us pass a current of electricity from a small voltaic circle along the nerve of a recently prepared frog; if the current be passed either in the direct or inverse directions, contractions are produced both at the closing and at the opening of the circuits. After a short time the effects (contractions) are produced only at the closing of the direct, and at the opening of the inverse current. I shall not enter upon the different results that are observed at various periods,

these have been noticed by Nobili and others, and especially by M. Chauveau. The results of my own observations lead me to believe that, after a short period, a series of constant results is not easily obtained, so that a doubt naturally arises whether any definite law can be laid down in regard to their production at distinct periods; nevertheless the facts, such as. I have stated to occur at the opening and closing of the circuits, will not, I think, be denied; and the question arises, can they be referred to any principle of action? M. Chauveau* and Dr Radcliffet suppose that muscular contractions are the result of instantaneous currents of high tension, the result of extra currents and induced currents formed at the opening and closing of the circuits. There can be no doubt that the change of state produced in the nerve occurs at these periods, and arises from an alteration in the electric tension of the circuits; but I believe also that the direction of the current traversing the nerve is of more importance. Let us suppose that we are acting upon a nerve after the first period of the excitability, when the effects (contractions) occur at the closing of the direct current, and not at its opening; and at the opening of the inverse current, and not at its closing. After the closure of the circuit, when the direct current is passing, we obtain contractions; but at its opening we then have an inverse current (the extra current), but no contractions. After the closure of the inverse current, no contractions; at its opening, we then obtain a direct current (extra current), and contractions are produced.

M. Chauveau has well pointed out the differences observed under these circumstances, but he speaks of the current as being stronger. Now, according to Faraday,‡ “the intensity and quantity of electricity moving in a current are smaller when the current commences, or is increased, and greater when it diminishes or closes;" such being the case, and if the results were due to high tension, we ought to have a greater effect at the opening of the direct current than at its closing, but experiment leads to an opposite conclusion. At the

* Journal de Physiologie, Janvier et Avril 1860.

On Epilepsy, 3d edit., 1861.

Experimental Researches, vol. i. para. 1107.

closing of the inverse current we get no effect; but at its opening, when we have the direct current (extra current), contractions are produced. From these facts, I cannot but infer that the direction of the current is of the utmost importance in these experiments; they go far to show an intimate connection between nerve force and electric force, but at the same time afford no proof of their identity.

The conclusions that are deduced from the foregoing experiments and arguments are,

First, That no inductive effect is obtained during nerve action upon a neighbouring nerve.

Secondly, The contractions which are observed in the limb secondarily excited may arise from various circumstances, which may be divided into those which are extrinsic and those which are intrinsic. Amongst the former are, 1st, The nerve-current; 2dly, From the electricity evolved during the contraction of the muscles; 3dly, From the extent of heterogeneous substances adhering to the nerve, or from a muscular current; 4thly, From the electricity employed to arouse the contractions in the limb; and, 5thly, From a change of condition (electric) in the nerve primarily excited. The intrinsic are, 1st, The state of the nerve respecting its dryness; and, 2dly, The state of the animal at the time of the experiment.

Thirdly, No inductive effect is produced upon the nerve when placed in the neighbourhood of a wire traversed by an electric current at the opening and breaking of the circuit.

Fourthly, That, in the application of the principle of conservation of force to the organic kingdom, other phenomena besides those connected with the development of heat and chemical action require to be studied; and,

Fifthly, In the action of electricity upon nerves to arouse muscular contraction, the direction of the current is of the utmost importance to be attended to.

17

Observations on the Natural History of the Enemies of the Coffee-Tree in Ceylon. By J. NEITNER, Esq., Ceylon.

In publishing these observations (which may be looked upon as a continuation of a general notice of noxious Ceylon insects, published by me in Stettiner Ent. Zeitung 1857), I have a twofold object in view: first, the diffusion of a correct knowledge of the subject which they embrace amongst my brother planters, and secondly to furnish a contribution to biographical and economic entomology-a branch of the science which is now being daily more and more appreciated. In judging of apparently trivial passages as well as of scientific technicalities, which occur in the text, this must be borne in mind. To those of my brother planters who would have wished for more elementary explanations than space permitted me to introduce, I can strongly recommend "Westwood's Introduction to the Modern Classification of Insects," 2 vols., with numerous woodcuts, as a most excellent and inexhaustive source of information.

The numerical list given below might easily be doubled by minute research in the outlying districts, and introduction of unimportant species. However, such as it is, it holds good for the entire coffee region of Ceylon in general, and for the cluster of districts grouped round the Peacock-hill (my special field of research) in particular. In fact, the brown and white bug, and the black and white grub, are the only universal and important enemies of the coffee-tree. The destructions of Arhines, Limacodes, Zeuzera, Phymatea, Strachia, and the coffee-rat, appear to be of a more local and occasional nature, and are therefore of less importance. The rest of the species. are nearly all enumerated for the sake of scientific completeness only. To the gentlemen, both here and in Europe, who have assisted me, I beg to tender my best thanks.

A few statistical notes will not be uninteresting to the reader abroad. The hill region of Ceylon covers an area of about 2000 square miles, is of a somewhat circular form, and its most elevated peaks rise to 8280 feet above the level of the sea. Systematic coffee planting is, from physiological reasons, exNEW SERIES.-VOL. XV. NO. I.-JAN. 1862.

C

clusively carried on in these hills, although irregular native garden-plantations are found everywhere in the island, even close to the sea-beach. The favourite elevation is between 1500 and 3500 feet, but in a few exceptional cases estates descend almost to the foot of the hills, whilst others are situated as high as 5500 feet and more. The number of systematically worked coffee estates, scattered all about these hills, amounts to about 420, divided amongst twenty-eight districts (very widely differing in some instances in physical aspect), covering an area of about 90,000 acres, producing about 600,000 cwts. of clean coffee (worth on the spot about £1,500,000 sterling), and giving employment to upwards of 100,000 persons, chiefly Tamil labourers from the coast of India. This is exclusive of about 50,000 acres of native coffee. It seems that the coffee-tree was brought to Ceylon by the Dutch, about two hundred years ago, but the first estate was only opened in 1825.

I now give a list of the names of the enemies of the coffeetree and their parasites (in which I have not thought it necessary to adhere strictly to systematic order), and then proceed to detailed descriptions.

List of the Enemies of the Coffee-Tree and their Parasites.

HEMIPTERA.

1. Pseudococcus Adonidum, L? (White or mealy bug). Parasites Scymnus rotundatus, Motch. Et. ent. 1859; Encyrtus Neitneri, Motch. loc. cit.; Chartocerus musciformis Motch. loc. cit.; Acarus translucens, N.

2. Lecanium coffee, Walk. List. Ins. B. M. (Brown or scaly bug).

Parasites: Scutellista cyanea, Motch. loc. cit.; Cephaleta purpureirentris, Motch. loc. cit.; C. brunneiventris, Motch. loc. cit.; C. fusciventris, Motch. in litt; Encyrtus paradisicus, Motch. in litt; E. Neitneri, Motch.; Cirrhospilus coccivorus, Motch. in litt; Marietta leopardina, N. in litt.; Chilocorus circumdatus, Schonh.; Acarus translucens, N.

3. Lecanium nigrum, N. (Black bug).

4. Syncladium Neitneri, Rabh. Dresd. Hedwig. 1858. Triposporium Gardneri, Berk. J. Hort. Soc. Lond. 1849. A fungus. 5. Aphis coffea N. (Coffee-louse).

Parasites: Syrphus Nietneri, Schiner in litt.; S. splendens,