162 Mr. Francis Gallon [April 25, 



first described by myself a year ago under the name of ' Composite 

 Portraits,' * and specimens of the latter will be exhibited. Tlien the 

 cause will be explained that renders the mind incompetent to blend 

 memories together in their just proportions. 



The physiological basis of memory is simple enough in its broad 

 outlines. Whenever any group of brain elements has been excited by 

 a sense impression, it becomes, so to speak, tender, and liable to be 

 easily thrown again into a similar state of excitement. If the new 

 cause of excitement differs from the original one, a memory is the 

 result. Whenever a single cause throws different groups of brain 

 elements simultaneously into excitement, the result must be a blended 

 memory. 



We are familiar with the fact that faint memories are very apt to 

 become confused. Thus some picture of mountain and lake in a 

 country which we have never visited, often recalls a vague sense of 

 identity with much we have seen elsewhere. Our recollections cannot 

 be disentangled, though general resemblances are recognized. It is 

 also a fact that the memories of persons who have great powers of 

 visualising, that is, of seeing well-defined images in the mind's eye, 

 are no less capable of being blended together. Artists are, as a class, 

 possessed of the visualising power in a high degree, and they are at 

 the same time pre-eminently distinguished by their gifts of generali- 

 zation. They are of all men the most capable of producing forms 

 that are not copies of any individual, but represent the characteristic 

 features of classes. 



There is then, no doubt, from whatever side the subject of memory 

 is approached, whether from the material or from the mental, and, in 

 the latter case, whether we examine the experiences of those in whom 

 the visualising faculty is faint or in whom it is strong, that the brain 

 has the capacity of blending memories together. Neither can there 

 be any doubt that general impressions are faint and perhaps faulty 

 editions of blended memories. They are subject to errors of their 

 own, and they inherit all those to which the memories are themselves 

 liable. 



Specimens of blended portraits will now be exhibited ; these might, 

 with more propriety, be named, according to the happy phrase of 

 Professor Huxley, " generic " portraits. The word generic presupposes 

 a genus, that is to say, a collection of individuals who have much 

 in common, and among whom medium characteristics are very much 

 more frequent than extreme ones. The same idea is sometimes 

 expressed by the word typical, which was much used by Quetelet, 

 who was the first to give it a rigorous interpretation, and whose idea 

 of a type lies at the basis of his statistical views. No statistician 

 dreams of combining objects into the same generic group that do not 

 cluster towards a common centre, no more can we compose generic 



* 'Journal of the Authropol. Institute' (Nov. 1878); or, 'Nature' (p. 97, 

 1878). 



