and brain has been acquired, that man does observe, and reason, construct hypotheses and cherish expectations, contemplate rules of conduct and regulate his actions in accordance with them, that scientific inquirers, attempting to include the whole range of human powers, have felt themselves urged forward to seek an explanation of the characteristics of mental life which are the familiar facts of man's experience. The course of _experiment_ has not brought them up to these facts; common acquaintance with them has pressed on scientific inquirers the need for dealing with them in order to make good the claim that science contains the explanation of all existence, man included. The dilemma for this conjecture that the brain thinks and wills is serious. If the brain is capable of what is commonly named _mental_ activity, all that science has demonstrated is susceptibility and motor activity, that is nerve impulse involving molecular and muscular action, and this carries no explanation of mental action. In this, as in previous cases, it is better to take purely scientific statements concerning the structure and functions of the nerve cells, without regard to theoretical result. The following quotations will show what account has been given of the variety of appearance and position of the nerve cells. Professor Turner says, nerve cells are "the characteristic structures in the nerve centres, are susceptible to impressions or nervous impulses, and are the texture in which the molecular changes occur that produce or disengage the special form of energy named nerve energy, the evolution of which is the distinctive mark of a nerve centre."[CY] "The central extremities of the nerve fibres lie in relation to, and are often directly connected with the nerve cells." From opposite points of the surface of the _bipolar cell_ "a strong process is given off, which is directly continued into a nerve fibre.[CZ]" When we pass next to _multipolar cells_, we have the following explanations. "In many localities they present characteristic forms. In the gray matter of the _spinal cord_, more especially in its anterior horn,[DA] they give rise to numerous processes, and have a stellate or radiate form. In the gray matter on the surface of the convolutions of the cerebrum they are pyramidal in shape; the apex is directed to the surface of the convolution, the base towards the white matter; the processes arise from the base, apex, and sides of the pyramid."[DB] "The processes which arise from a multipolar nerve cell as a rule divide and subdivide as they pass away from the body of the cell, until at last they give rise to branches of extreme tenuity. These branching processes apparently consist exclusively of cell protoplasm, and have been called protoplasm processes. Gerlach has described the protoplasm processes of the multipolar nerve cells of the brain and spinal cord as forming an excessively minute net-work, from which