“But this does not mean that all methods, or any single method, arrived at by scientific and technical research offers every moral guarantee. Nor, moreover, does it mean that every method becomes licit because it increases and deepens our knowledge. Sometimes it happens that a method cannot be used without injuring the rights of others or without violating some moral rule of absolute value. In such a case, although one rightly envisages and pursues the increase of knowledge, morally the method is not admissible. Why not? Because science is not the highest value, that to which all other orders of values-or in the same order of value, all particular values-should be subordinated. Science itself, therefore, as well as its research and acquisitions, must be inserted in the order of values. Here there are well defined limits which even medical science cannot transgress without violating higher moral rules. The confidential relations between doctor and patient, the personal right of the patient to the life of his body and soul in its psychic and moral integrity are just some of the many values superior to scientific interest.”

“In the first place it must be assumed that, as a private person, the doctor can take no measure or try no course of action without the consent of the patient. The doctor has no other rights or power over the patient than those which the latter gives him, explicitly or implicitly and tacitly. On his side, the patient cannot confer rights he does not possess. In this discussion the decisive point is the moral licitness of the right a patient has to dispose of himself. Here is the moral limit to the doctor’s action taken with the consent of the patient.”

“As for the patient, he is not absolute master of himself, of his body or of his soul. He cannot, therefore, freely dispose of himself as he pleases. Even the reason for which he acts is of itself neither sufficient nor determining. The patient is bound to the immanent teleology laid down by nature. He has the right of use, limited by natural finality, of the faculties and powers of his human nature. Because he is a user and not a proprietor, he does not have unlimited power to destroy or mutilate his body and its functions...Thus, for example, a man cannot perform on himself or allow doctors to perform acts of a physical or somatic nature which doubtless relieve heavy physical or psychic burdens or infirmities, but which bring about at the same time permanent abolition or considerable and durable diminution of his freedom, that is, of his human personality in its typical and characteristic function. Such an act degrades a man to the level of a being reacting only to acquired reflexes or to a living automation. The moral law does not allow such a reversal of values. Here it sets up its limits to the “medical interests of the patient...In order to rid himself of repressions, inhibitions or psychic complexes man is not free to arouse in himself for therapeutic purposes each and every appetite of a sexual order which is being excited or has been excited in his being, appetites whose impure waves flood his unconscious or subconscious mind. He cannot make them the object of his thoughts and fully conscious desires with all the shocks and repercussions such a process entails. For a man and a Christian there is a law of integrity and personal purity, of self-respect, forbidding him to plunge so deeply into the world of sexual suggestions and tendencies.”

“We have answered the question: Where does the doctor find a moral limit in research into and use of new methods and procedures in the “interests of the patient?” The limit is the same as that for the patient...The limit is the same for the doctor as for the patient because, as We have already said, the doctor as a private individual disposes only of the rights given him by the patient and because the patient can give only what he himself possesses.”

For the complete encyclical, it can be read here

“Venerable Brethren, however much we may pity the mother whose health and even life is gravely imperiled in the performance of the duty allotted to her by nature, nevertheless what could ever be a sufficient reason for excusing in any way the direct murder of the innocent? This is precisely what we are dealing with here. Whether inflicted upon the mother or upon the child, it is against the precept of God and the law of nature: “Thou shalt not kill: ”The life of each is equally sacred, and no one has the power, not even the public authority, to destroy it. It is of no use to appeal to the right of taking away life for here it is a question of the innocent, whereas that right has regard only to the guilty; nor is there here question of defense by bloodshed against an unjust aggressor (for who would call an innocent child an unjust aggressor?); again there is not question here of what is called the “law of extreme necessity” which could even extend to the direct killing of the innocent. Upright and skillful doctors strive most praiseworthily to guard and preserve the lives of both mother and child; on the contrary, those show themselves most unworthy of the noble medical profession who encompass the death of one or the other, through a pretense at practicing medicine or through motives of misguided pity.”

"In the above mentioned cases, insofar as the moral justification of the experiments rests on the mandate of public authority, and therefore on the subordination of the individual to the community, of the individual’s welfare to the common welfare, it is based on an erroneous explanation of this principle. It must be noted that, in his personal being, man is not finally ordered to usefulness to society. On the contrary, the community exists for man.”