In animals hormones secreted by the endocrine glands produce a wide range of body reactions. These however do not determine the sex but rather influence in the proper functioning of sex.
For instance lack of proper hormones may render an individual sterile even though the individual may be structurally either male or female. Hormones control the secondary sexual characters (sex differentiation or functioning of the sex) rather than the primary sexual characters (structural sex).
Chromosomes determine whether an individual should be male or female structurally, while hormones decide whether the individual should function as male or female.
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In other words chromosomes decide the development of either ovary or testis, while the hormones control their function as effective male and female reproductive organs.
The hormones produced by the gonads (male and female) are distributed all over the body inducing the secondary sexual characters the influence of hormones as secondary sexual characters may be studied with the help of examples like partial sex reversals.
In partial sex reversal, a male or female individual may be made to develop a few characters of the opposite sex by injecting appropriate hormones.
In Salamander, grafting between male (upper part) and female (lower part) would produce the individual with suppressed ovaries. The male hormone coming from medulla suppresses the ovaries.
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Walker, in his experiments with poultry has shown that a testicular extract from a rooster, when injected into a hen would make her (hen) produce a comb.
It has also been observed that generally egg laying hen, when they grow old begin to show characters of male and may even develop comb and start crowing.