at intervals. A sheath, apparently representing the neurilemma, is however present in each fibre.

The optic "nerve" is also properly speaking a lobe of the brain, and it retains its character as a part of the central nervous system in so far as its fibres have no neurilemma and are nodeless, but it contains no nerve cells along its course.

APPENDIX.

ANATOMICAL AND PHYSIOLOGICAL CONSTANTS.

THE weight of the body of a full-grown man may be taken at 154 lbs.

away

Water

Solid matters

21

II

1471

The addition of 7 lbs. of blood, the quantity which will readily drain from the body, will bring the total to 154 lbs. A considerable quantity of blood will, however, always remain in the capillaries and small blood. vessels, and must be reckoned with the various tissues. The total quantity of blood in the body is now calculated at about 1-13th of the body weight. i.e. about 12 lbs.

The solids would consist of the elements oxygen, hy. drogen, carbon, nitrogen, phosphorus, sulphur, silicon, chlorine, fluorine, potassium, sodium, calcium (lithium), magnesium, iron (manganese copper, lead), and may be arranged under the heads of

Proteids. Carbo-hydrates or Amyloids.

Fats.

Minerals.

Such a body would lose in 24 hours-of water, about 40,000 grains, or 6 lbs.; of other matters about 14,500 grains, or over 2 lbs. ; among which of carbon 4,000 grains, or more than lb.; of nitrogen 300 grains; of mineral matters 400 grains; and would part, per diem, with as much heat as would raise 8,700 lbs. of water from 0° to 1° Fahr., which is equivalent to 3,000 foot-tons.1 Such a body ought to do as much work as is equal to 450 foot-tons.

The losses would occur through various organs, thus

-by

The gains and losses of the body would be as follows :

Creditor-Solid dry food

grs.

8,4co

10,000

high.

36,100

54,500

grs. 40,000

14,500

54,500

A foot-ton is the equivalent of the work required to lift one ton one foot

II. DIGESTION.

Such a body would require for daily food, carbon 4,000 grains, nitrogen 300 grains.

Now proteids contain, in round numbers, about 15 per cent. nitrogen, and 50 per cent. carbon, while carbohydrates and fats contain respectively 40 per cent. and 80 per cent. carbon. Hence the necessary amounts of nitrogen and carbon, together with the other necessary elements, might be obtained as follows :

Proteids

2,000 grs. containing 300 grs. nitrogen 1,000 grs. carbon.

which, in turn, might be obtained, for instance, by means

This table, however, must be understood as being introduced for the sake of illustration only.

The fæces passed, per diem, would amount to about 2,800 grains, containing solid matter 800 grains.