The simple elementary forms are first received: these in course of time, according to the cerebral capacity, are compounded until the individual has attained by educational experience sufficient information to use the highest brain function, namely, of knowing the relations between cause and effect.

There are other conditions necessary in order that the brain function should be exercised with power - the supply of nervous fluid by the lungs must be adequate to the expenditure.

It has been shown that some persons resort to stimulants in order to excite brain function in consequence of a natural sluggishness. This abnormal excitement, though at first it may be attended with beneficial results, ultimately destroys the mental powers, as constantly increased doses are demanded in order to produce like effects.

When the anaesthetics are inhaled, the productive function of the lungs is so great, and the supply to the brain so sudden, that a nervous congestive state is the consequence. If, however, small quantities are inhaled, there is merely an exciting or stimulation of the cerebral functions. The most effective stimulating vapours are those which act on the nervous filaments of the lungs, exciting them to increased functional action in the production of the nervo-vital fluid. In this particular none surpass the action of protoxide of nitrogen. It has this most important advantage, that it does not interfere with or destroy the composition of the blood, which is invariably the case when the chlorine and carbon compounds are inhaled. It is true that the venous blood is prevented in a great measure from throwing off its carbon with freedom, in consequence of the increased action of the nervous tissue contracting the mouths of the venous capillaries. This is, however, a condition which must exist with all anaesthetics which act promptly on the brain in producing nervous congestion. The nitrous oxide does not destroy the nervo-muscular tone of the heart, which is always liable to be paralysed in the inhalation of the chlorine and carbon anaesthetics.

All substances which have a tendency to disintegrate the natural component parts of the blood should be avoided. When the vitiated blood comes in contact with the walls of the heart, it negatives the nervous influence derived from the cardiac plexus. If it does not suspend its contractile powers, it oftentimes lays the foundation of future morbid functional derangement.

We must now re-occupy ourselves with the consideration of Vital Photography.

There is abundant evidence that the nervous vibratory shock of the mother is communicated to the body of the child, conveying under favourable conditions, a faithful embodiment of the impression which has caused such an emotional paroxysm. When the Egyptian magician was asked what class of persons were susceptible to the action of the narcotic fumes, he replied, "A boy under puberty, a "virgin, a black female slave, and a pregnant woman."

It is well known that during the early periods of pregnancy some women are peculiarly susceptible to influences which do not affect them at other times; the whole nervous system seems to be thrown into a state of abnormal excitement. During this period, any powerful mental shock will be conveyed to the foetus.

The following cases will exhibit how the nervous vibratory configurations are conveyed from the brain to the liquor amnii, and thence to the sensitive nervous surface of the child.

Case 1. - Whilst in Grass Valley, Nevada County, California, in 1852, General G. showed the author the representation or counterpart of a large green snake which encircled his body. The explanation of this phenomenon was that his mother when four months pregnant with the General, was present when one of the negroes on the plantation, having killed a snake, had put it round his waist in bravado. On Madame G. seeing this, she was so powerfully impressed as to swoon or lose consciousness, and on the birth of the child, the figure of the snake was found to be not only photographed, but embodied on the child. It is a curious fact, that in the spring of the year, when these snakes recover from a state of torpor in which they remain during the winter months, the snake impression on the General increased in size and' rotundity, and assumed a vivid green colour, which disappeared during the autumn and winter months.

Case 2. - A lady during the fourth month of pregnancy saw a large Newfoundland dog destroy a lamb. On the birth of the child it had a sheep's countenance, and a plentiful growth of wool on the back.

Case 3. - In crossing the American plains (1850) from the Atlanic to the Pacific coast, a lady who was pregnant had ridden on a mule for over four months. A short time after delivery in San Francisco, the right arm of the child was continually in motion, as if in the act of using a whip, which corresponded with the motion of the mother's arm during her pregnancy, flogging the mule. This movement continued for two years.

Case 4. - A pregnant woman, in Deptford, was frightened by a monkey. On giving birth, the child's face was an exact counterpart of the animal. The shock on the poor woman was such, that in two subsequent confinements her children had the monkey physiognomy. Injuries to the nervous system are often propagated.

Case 5. - A woman in the third month of pregnancy was frightened by a large black dog playfully jumping on her. The shock was so great that in a few weeks subsequent she miscarried, the foetus having the head of a dog.

Case 6. - A lady in the second month of pregnancy was frightened so much as to be deprived of consciousness, in consequence of a mouse jumping on her shoulder from a cupboard. On the birth of the child, the prototype of the mouse was embodied on the shoulder.

A strong desire, or longing unsatisfied in a pregnant woman, will oftentimes be impressed on the offspring.

Case 7. - My own brother has a salmon depicted on his thigh. The miniature fish is complete, even to the colour, which is particularly vivid during the period this fish is in season.

Brain shocks are productive of the same results in the lower animals.

In June, 1870, at the country seat of Mr. Ellmore, near Calais, a favourite rabbit, which had been reared in an unoccupied stable or out-house, was frightened by the entrance of a sheep. In littering some twenty-five days after, one of the young rabbits had a sheep's head.

Another case is that of a sow, who, being alarmed at the sight of an elephant, gave birth to a young pig, with an elephant's head, with proboscis complete. This lusus natures was a Cyclops, having only one eye in the centre of the forehead. The specimen is in the Museum of the Paris School of Medicine.