Book excerpt: During the last decade research on neural transplantation in mammals has grown extensively, and has attracted the attention of many young inquisitive scientists. This growth, as the critics point out, has been somewhat random, and has resulted neither in the formulation of basic concepts nor in any other significant achievement. For instance, they question-how is it possible to jump into functional research with clinical bearing when the basic morphological work has not yet been conducted? The criticism, objectively speaking, is valid and is supported by the fact that every investigator who has stepped into this unex plored field of neurosciences has formulated questions in his own way, has followed his own "model" oftransplantation, and has arrived at his own unique conclusions. The potential danger, as the critics emphasize, in this type of approach lies in that instead of evolving into a scientifically solid and valuable field of research, it may end in a confusing and conflicting mass of questionable claims and subjective opinions. The present situation, very likely, is a reflection of unrestrained enthusiasm and imaginativeness of the investigators, and the demands of the times for the so-called "newsworthy" and "breakthrough" publications. Despite these limitations, two important facts have been estab lished in this field. First, as far as transplantation of neural tissues per se is concerned, what was considered impossible by some critics about 10-12 years ago has been shown to be possible.