Well-washed and well-combed domestic pets grow dull they miss the stimulus of fleas.

Eugenics is the study of the agencies under social control that may improve or impair the racial qualities of future generations either physically or mentally.

Exercising the right of occasional suppression and slight modification, it is truly absurd to see how plastic a limited number of observations become, in the hands of men with preconceived ideas.

The conditions that direct the order of . . . the living world . . . are marked by their persistence in improving the birthright of successive generations.

Whenever you can, count.

The object . . . is to discover methods of condensing information concerning large groups of allied facts into brief and compendious expressions suitable for discussion.

[Statistics are] the only tools by which an opening can be cut through the formidable thicket of difficulties that bars the path of those who pursue the Science of Man.

All male animals, including men, when they are in love, are apt to behave in ways that seem ludicrous to bystanders.

Characteristics cling to families.

The cat is the only non-gregarious domestic animal. It is retained by its extra-ordinary adhesion to the comforts of the house in which it is reared.

The inferiority of photographs to the best works of artists, so far as resemblance is concerned, lies in their catching no more than a single expression. If many photographs of a person were taken at different times, perhaps even years apart, their composite would possess that in which a single photograph is deficient.