So you've made a human centipede. Now that you have achieved your ultimate creature creation and almost clinched that position with the Legion of Doom I need to let you in on the expensive and tedious upkeep of your new "pet."
(If you are confused at this point, Human Centipede First Sequence is an independent horror flick about a German doctor who was internationally famous for separating Siamese twins. He retired to his own demented experiment: linking animals or people anus to mouth to form a "centipede". You really should watch it. I found it hilarious, creepy, and inspirational while not being terribly graphic or a gore fest.)
* Each segment will need an open port for medications, fluids and parenteral nutrition. The port will need to be placed where it will be hard for the free arms of the 'pede to pull it out. You may even need some form or restraint that allows arms movement for walking but not enough movement to reach out and damage itself or others.
* Antibiotic therapy. You have essentially linked a rectal cesspool of bacterial activity to a human mouth & throat which leaves many opportunities for disaster. You will need serious antibiotic therapy for several months while the GI tracts "merge" and the surgical wounds heal.
* Antacids and anti emetics. "Segments" will need antacid therapy to prevent ulceration of the merging GI tracts while the anti emetic will prevent the risk of aspiration pneumonia if a "segment" regurgitates when the segment in front of it defecates.
* You will need to assess the fluid, caloric, and vitamin needs of each "segment" and fulfill them with parenteral nutrition. The merging GI tracts will not function at normal capacity and will need time to heal. You will also have to start with an oral liquid diet and slowly work up to solids as the healing continues. It would be such a waste if your creation died from malnutrition before it was even completely healed. Even after healing the middle and tail segments may need parenteral supplementation in order to maintain health.
* You will need to flush the ports on a regular basis to prevent bacterial growth and "crust" that could lead to a potentially fatal blood clot. The loss of one segment could be devastating for the 'pede as a whole.
* Mental health. It is going to be a task of Herculean proportion to get each "segment" to perform and succumb to the will of the whole. Humans tend to be stubborn and their will to survive unstoppable. It may take many weeks of benzodiazepines and antidepressants to bend the will of the "segments" to become the "whole." If you want to go a faster route I would recommend frontal lobotomy for all but the lead segment. Your 'pede will be easier to train when lucid.
* Housebreaking. Since each segment will need to urinate housebreaking will be essential to a cohesive and happy home environment. Cage training is the easiest. Follow the same procedure as if you were housebreaking a dog. Otherwise you will have to devise a diaper to fit the new configuration of the back end with exception of the tail "segment" which should do just fine with Depends.
* Hygiene. Since some of your "segments" are female you might want to give hormone therapy to prevent menstruation or consider hysterectomy to prevent a bloody mess each month. You will also have to bathe your 'pede on a regular basis and use deodorant for underarms.
* You will need to design a "shoe" to protect the dragging parts below the knees and to cushion the knees which will be supporting the brunt of the weight. It may even be necessary for amputation below the knee to prevent issues with poor circulation and blood clotting.
As you can see it isn't enough to just create the human centipede but to carefully and expensively care for your centipede to make it a happy, healthy, show-stopping part of your demented genius that would make even Mary Shelley proud to witness.